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[[Category:Troubleshooting]]
= Sniffer Troubleshooting =
[[Category:Sniffer]]
{{DISPLAYTITLE:Troubleshooting: No Calls Being Sniffed}}


'''This guide provides a systematic, step-by-step process to diagnose why the VoIPmonitor sensor might not be capturing any calls. Follow these steps in order to quickly identify and resolve the most common issues.'''
This page covers common VoIPmonitor sniffer/sensor problems organized by symptom. For configuration reference, see [[Sniffer_configuration]]. For performance tuning, see [[Scaling]].


== Troubleshooting Flowchart ==
== Critical First Step: Is Traffic Reaching the Interface? ==


<kroki lang="mermaid">
{{Warning|Before any sensor tuning, verify packets are reaching the network interface. If packets aren't there, no amount of sensor configuration will help.}}
%%{init: {'theme': 'base', 'flowchart': {'nodeSpacing': 10, 'rankSpacing': 25, 'curve': 'basis'}, 'themeVariables': {'fontSize': '11px'}}}%%
flowchart TD
    A[Sensor Not Working Properly] --> B{Service Running?}
    B -->|No| B1[systemctl restart voipmonitor]
    B -->|Yes| C{Calls Missing?}
 
    C -->|Yes| D{Step 2: Traffic on Interface?<br/>tshark -i eth0 -Y 'sip'}
    D -->|No packets| E[Step 3: Network Issue]
    E --> E1{Interface UP?}
    E1 -->|No| E2[ip link set dev eth0 up]
    E1 -->|Yes| E3{SPAN/RSPAN?}
    E3 -->|Yes| E4[Enable promisc mode]
    E3 -->|ERSPAN/GRE/TZSP| E5[Check tunnel config]
 
    D -->|Packets visible| F[Step 4: VoIPmonitor Config]
    F --> F1{interface correct?}
    F1 -->|No| F2[Fix interface in voipmonitor.conf]
    F1 -->|Yes| F3{sipport correct?}
    F3 -->|No| F4[Add port: sipport = 5060,5080]
    F3 -->|Yes| F5{BPF filter blocking?}
    F5 -->|Maybe| F6[Comment out filter directive]


    F5 -->|No| G[Step 5: GUI Capture Rules]
    G --> G1{Rules with Skip: ON?}
    G1 -->|Yes| G2[Remove/modify rules + reload sniffer]
    G1 -->|No| H[Step 6: Check Logs]
    H --> I{OOM or Packetbuffer?}
    I -->|OOM Events| I1[Step 7: Add RAM / tune MySQL]
    I -->|PACKETBUFFER FULL| I2[Step 8: Increase threading and max_buffer_mem]
    I -->|Neither| J{Large SIP packets?}
    J -->|Yes| J1{External SIP source?<br/>Kamailio/HAProxy mirror}
    J1 -->|No| J2[Step 9: Increase snaplen]
    J1 -->|Yes| J3[Fix external source: Kamailio siptrace or HAProxy tee]
    J -->|No| K[Contact Support]
</kroki>
== Post-Reboot Verification Checklist ==
After a planned server reboot, verify these critical items to ensure VoIPmonitor operates correctly. This check helps identify issues that may occur when configurations are not persisted across reboots.
=== Verify Firewall/Iptables Rules ===
After a system restart, verify that firewall rules have been correctly applied and are allowing necessary traffic. Firewall rules may need to be manually re-applied if they were not made persistent.
;1. Check current firewall status:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For systems using iptables
# Check for SIP traffic on the capture interface
iptables -L -n -v
tcpdump -i eth0 -nn "host <PROBLEMATIC_IP> and port 5060" -c 10
 
# For systems using firewalld
firewall-cmd --list-all


# For systems using ufw
# If no packets: Network/SPAN issue - contact network admin
ufw status verbose
# If packets visible: Proceed with sensor troubleshooting below
</syntaxhighlight>
</syntaxhighlight>


;2. Verify critical ports are allowed:
<kroki lang="mermaid">
Ensure the firewall permits traffic on the following VoIPmonitor ports:
graph TD
* SIP ports (default: 5060/udp, or your configured sipport values)
    A[No Calls Recorded] --> B{Packets on interface?<br/>tcpdump -i eth0 port 5060}
* RTP ports (range used by your PBX)
    B -->|No packets| C[Network Issue]
* GUI access (typically: 80/tcp, 443/tcp)
    C --> C1[Check SPAN/mirror config]
* Sensor management port: 5029/tcp
    C --> C2[Verify VLAN tagging]
* Client-Server connection port: 60024/tcp (for distributed setups)
    C --> C3[Check cable/port]
    B -->|Packets visible| D[Sensor Issue]
    D --> D1[Check voipmonitor.conf]
    D --> D2[Check GUI Capture Rules]
    D --> D3[Check logs for errors]
</kroki>


;3. Make firewall rules persistent:
== Quick Diagnostic Checklist ==
To prevent firewall rules from being lost after future reboots:


'''For iptables (Debian/Ubuntu):'''
{| class="wikitable"
<syntaxhighlight lang="bash">
|-
# Save current rules
! Check !! Command !! Expected Result
iptables-save > /etc/iptables/rules.v4
|-
# Install persistent package if not present
| Service running || <code>systemctl status voipmonitor</code> || Active (running)
apt-get install iptables-persistent
|-
</syntaxhighlight>
| Traffic on interface || <code>tshark -i eth0 -c 5 -Y "sip"</code> || SIP packets displayed
|-
| Interface errors || <code>ip -s link show eth0</code> || No RX errors/drops
|-
| Promiscuous mode || <code>ip link show eth0</code> || PROMISC flag present
|-
| Logs || <code>tail -100 /var/log/syslog \| grep voip</code> || No critical errors
|-
| GUI rules || Settings → Capture Rules || No unexpected "Skip" rules
|}


'''For firewalld (CentOS/RHEL):'''
== No Calls Being Recorded ==
<syntaxhighlight lang="bash">
# Runtime rules automatically persist with --permanent flag
firewall-cmd --permanent --add-port=5060/udp
firewall-cmd --permanent --add-port=60024/tcp
firewall-cmd --reload
</syntaxhighlight>


=== Verify System Time Synchronization ===
=== Service Not Running ===


Correct system time synchronization is '''critical''', especially when using the <code>packetbuffer_sender</code> option in distributed architectures. Time mismatches between hosts and servers can cause call correlation failures and dropped packets.
;1. Check current NTP/chrony status:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For systems using NTP
# Check status
ntpstat
systemctl status voipmonitor


# For systems using chrony
# View recent logs
chronyc tracking
journalctl -u voipmonitor --since "10 minutes ago"
</syntaxhighlight>


;2. Verify time synchronization with servers:
# Start/restart
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
# For NTP
ntpq -p
 
# For chrony
chronyc sources -v
</syntaxhighlight>
 
'''Expected output:''' Time offset should be minimal (ideally under 100 milliseconds). Large offsets (several seconds) indicate synchronization problems.
 
;3. Manual sync if needed (temporary fix):
<syntaxhighlight lang="bash">
# Force immediate NTP sync
sudo systemctl restart ntp
 
# For chrony
sudo chronyc makestep
</syntaxhighlight>
 
'''Critical for packetbuffer_sender mode:''' When using <code>packetbuffer_sender=yes</code> to forward raw packets from remote sensors to a central server, the host and server '''must have synchronized times'''. VoIPmonitor requires host and server times to match for proper call correlation and packet processing. Maximum allowed time difference is 2 seconds by default (configurable via <code>client_server_connect_maximum_time_diff_s</code>).
 
;4. Check distributed architecture time sync:
In Client-Server mode, ensure all sensors and the central server are synchronized to the same NTP servers:
 
<syntaxhighlight lang="bash">
# On each sensor and central server
timedatectl status
</syntaxhighlight>
</syntaxhighlight>


Look for: <code>System clock synchronized: yes</code>
Common startup failures:
 
* '''Interface not found''': Check <code>interface</code> in voipmonitor.conf matches <code>ip a</code> output
If times are not synchronized across distributed components:
* '''Port already in use''': Another process using the management port
* Verify all systems point to the same reliable NTP source
* '''License issue''': Check [[License]] for activation problems
* Check firewall allows UDP port 123 (NTP)
* Ensure timezones are consistent across all systems
 
'''Troubleshooting time sync issues:'''
* Check firewall rules allow NTP (UDP port 123)
* Verify NTP servers are reachable: <code>ping pool.ntp.org</code>
* Review NTP configuration: <code>/etc/ntp.conf</code> or <code>/etc/chrony.conf</code>
* Ensure time service is enabled to start on boot: <code>systemctl enable ntp</code>


== Step 1: Is the VoIPmonitor Service Running Correctly? ==
=== Wrong Interface or Port Configuration ===
First, confirm that the sensor process is active and loaded the correct configuration file.


;1. Check the service status (for modern systemd systems):
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
systemctl status voipmonitor
# Check current config
</syntaxhighlight>
grep -E "^interface|^sipport" /etc/voipmonitor.conf
Look for a line that says <code>Active: active (running)</code>. If it is inactive or failed, try restarting it with <code>systemctl restart voipmonitor</code> and check the status again.


;2. Verify the running process:
# Example correct config:
<syntaxhighlight lang="bash">
# interface = eth0
ps aux | grep voipmonitor
# sipport = 5060
</syntaxhighlight>
</syntaxhighlight>
This command will show the running process and the exact command line arguments it was started with. Critically, ensure it is using the correct configuration file, for example: <code>--config-file /etc/voipmonitor.conf</code>. If it is not, there may be an issue with your startup script.
=== Troubleshooting: Missing Package or Library Dependencies ===
If the sensor service fails to start or crashes immediately with an error about a "missing package" or "missing library," it indicates that a required system dependency is not installed on the server. This is most common on newly installed sensors or fresh operating system installations.


;1. Check the system logs for the specific error message:
{{Tip|For multiple SIP ports: <code>sipport = 5060,5061,5080</code>}}
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
tail -f /var/log/syslog | grep voipmonitor


# For CentOS/RHEL/AlmaLinux or systemd systems
=== GUI Capture Rules Blocking ===
journalctl -u voipmonitor -f
</syntaxhighlight>


;2. Common missing packages for sensors:
Navigate to '''Settings → Capture Rules''' and check for rules with action "Skip" that may be blocking calls. Rules are processed in order - a Skip rule early in the list will block matching calls.
Most sensor missing package issues are resolved by installing the <code>rrdtools</code> package. This is required for RRD (Round-Robin Database) graphing and statistics functionality.


<syntaxhighlight lang="bash">
See [[Capture_rules]] for detailed configuration.
# For Debian/Ubuntu
apt-get update && apt-get install rrdtool


# For CentOS/RHEL/AlmaLinux
=== SPAN/Mirror Not Configured ===
yum install rrdtool
# OR
dnf install rrdtool
</syntaxhighlight>


;3. Other frequently missing dependencies:
If <code>tcpdump</code> shows no traffic:
If the error references a specific shared library or binary, install it using your package manager. Common examples:
# Verify switch SPAN/mirror port configuration
# Check that both directions (ingress + egress) are mirrored
# Confirm VLAN tagging is preserved if needed
# Test physical connectivity (cable, port status)


* <code>libpcap</code> or <code>libpcap-dev</code>: Packet capture library
See [[Sniffing_modes]] for SPAN, RSPAN, and ERSPAN configuration.
* <code>libssl</code> or <code>libssl-dev</code>: SSL/TLS support
* <code>zlib</code> or <code>zlib1g-dev</code>: Compression library


;4. Verify shared library dependencies:
=== Filter Parameter Too Restrictive ===
If the error mentions a specific shared library (e.g., <code>error while loading shared libraries: libxxx.so</code>), check which libraries the binary is trying to load:


<syntaxhighlight lang="bash">
If <code>filter</code> is set in voipmonitor.conf, it may exclude traffic:
ldd /usr/local/sbin/voipmonitor | grep pcap
</syntaxhighlight>


If <code>ldd</code> reports "not found," install the missing library using your package manager.
;5. After installing the missing package, restart the sensor service:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
# Check filter
systemctl status voipmonitor
grep "^filter" /etc/voipmonitor.conf
</syntaxhighlight>


Verify the service starts successfully and is now <code>Active: active (running)</code>.
# Temporarily disable to test
 
# Comment out the filter line and restart
=== Troubleshooting: Cron Daemon Not Running ===
 
If the VoIPmonitor sniffer service fails to start or the sensor appears unavailable despite the systemd service being configured correctly, the cron daemon may not be running. Some VoIPmonitor deployment methods and maintenance scripts rely on cron for proper initialization and periodic tasks.
 
;1. Check the cron daemon status:
<syntaxhighlight lang="bash">
systemctl status cron
</syntaxhighlight>
</syntaxhighlight>


Look for <code>Active: active (running)</code>. If the status shows inactive or failed, the cron daemon is not running.


;2. Alternative check for systems using cron (not crond):
<syntaxhighlight lang="bash">
systemctl status crond
</syntaxhighlight>


Note: On CentOS/RHEL systems, the service is typically named <code>crond</code>, while on Debian/Ubuntu systems it is named <code>cron</code>.
==== Missing id_sensor Parameter ====


;3. Start the cron daemon if it is inactive:
'''Symptom''': SIP packets visible in Capture/PCAP section but missing from CDR, SIP messages, and Call flow.
<syntaxhighlight lang="bash">
# For Debian/Ubuntu systems
systemctl start cron


# For CentOS/RHEL/AlmaLinux systems
'''Cause''': The <code>id_sensor</code> parameter is not configured or is missing. This parameter is required to associate captured packets with the CDR database.
systemctl start crond
</syntaxhighlight>


;4. Enable cron to start automatically on boot:
'''Solution''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For Debian/Ubuntu systems
# Check if id_sensor is set
systemctl enable cron
grep "^id_sensor" /etc/voipmonitor.conf


# For CentOS/RHEL/AlmaLinux systems
# Add or correct the parameter
systemctl enable crond
echo "id_sensor = 1" >> /etc/voipmonitor.conf
</syntaxhighlight>


;5. After starting the cron daemon, restart the VoIPmonitor service:
# Restart the service
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
systemctl restart voipmonitor
systemctl status voipmonitor
</syntaxhighlight>
</syntaxhighlight>


Verify the service now shows <code>Active: active (running)</code> and the sensor becomes visible in the GUI.
{{Tip|Use a unique numeric identifier (1-65535) for each sensor. Essential for multi-sensor deployments. See [[Sniffer_configuration#id_sensor|id_sensor documentation]].}}
== Missing Audio / RTP Issues ==


=== Root Cause ===
=== One-Way Audio (Asymmetric Mirroring) ===
The cron daemon being inactive can prevent VoIPmonitor from starting properly in scenarios where:
* Installation scripts use cron for post-install configuration
* Maintenance or cleanup jobs are required for proper sensor operation
* System initialization processes depend on cron-based tasks
* The sensor was recently rebooted or upgraded and cron failed to start


=== Long-Term Stability ===
'''Symptom''': SIP recorded but only one RTP direction captured.
If the cron daemon is consistently failing to start after reboots:
* Check system logs for cron startup errors: <code>journalctl -u cron -n 50</code> or <code>journalctl -u crond -n 50</code>
* Verify that the server has sufficient resources (CPU, memory) to run all required system services
* Investigate performance bottlenecks that may be causing system services to fail to start
* Ensure no other system services are conflicting or preventing cron from starting


== Step 2: Is Network Traffic Reaching the Server? ==
'''Cause''': SPAN port configured for only one direction.
If the service is running, the next step is to verify if the VoIP packets (SIP/RTP) are actually arriving at the server's network interface. The best tool for this is <code>tshark</code> (the command-line version of Wireshark).


;1. Install tshark:
'''Diagnosis''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
# Count RTP packets per direction
apt-get update && apt-get install tshark
tshark -i eth0 -Y "rtp" -T fields -e ip.src -e ip.dst | sort | uniq -c
 
# For CentOS/RHEL/AlmaLinux
yum install wireshark
</syntaxhighlight>
</syntaxhighlight>


;2. Listen for SIP traffic on the correct interface:
If one direction shows 0 or very few packets, configure the switch to mirror both ingress and egress traffic.
Replace <code>eth0</code> with the interface name you have configured in <code>voipmonitor.conf</code>.
<syntaxhighlight lang="bash">
tshark -i eth0 -Y "sip || rtp" -n
</syntaxhighlight>
* '''If you see a continuous stream of SIP and RTP packets''', it means traffic is reaching the server, and the problem is likely in VoIPmonitor's configuration (see Step 4).
* '''If you see NO packets''', the problem lies with your network configuration. Proceed to Step 3.


== Step 3: Troubleshoot Network and Interface Configuration ==
=== RTP Not Associated with Call ===
If <code>tshark</code> shows no traffic, it means the packets are not being delivered to the operating system correctly.


;1. Check if the interface is UP:
'''Symptom''': Audio plays in sniffer but not in GUI, or RTP listed under wrong call.
Ensure the network interface is active.
<syntaxhighlight lang="bash">
ip link show eth0
</syntaxhighlight>
The output should contain the word <code>UP</code>. If it doesn't, bring it up with:
<syntaxhighlight lang="bash">
ip link set dev eth0 up
</syntaxhighlight>


;2. Check for Interface Packet Drops:
'''Possible causes''':
If calls are missing, showing "000" as the last response, or have silent audio, the root cause may be packets being dropped at the '''network interface level''' BEFORE they reach VoIPmonitor. This is different from sensor resource limitations.


Check the interface statistics for packet drops on the sniffing interface:
'''1. SIP and RTP on different interfaces/VLANs''':
 
<syntaxhighlight lang="ini">
<syntaxhighlight lang="bash">
# voipmonitor.conf - enable automatic RTP association
# Check detailed interface statistics, packet errors, and drops
auto_enable_use_blocks = yes
ip -s -s l l eth0
</syntaxhighlight>
</syntaxhighlight>


The output shows RX (receive) and TX (transmit) statistics. Look specifically at the <code>dropped</code> counter under the <code>RX</code> section:
'''2. NAT not configured''':
<syntaxhighlight lang="ini">
# voipmonitor.conf - for NAT scenarios
natalias = <public_ip> <private_ip>


<syntaxhighlight lang="text">
# If not working, try reversed order:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
natalias = <private_ip> <public_ip>
    link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    12345123  45678    12      5432    0      0
    TX: bytes  packets  errors  dropped carrier collsns
    9876543  23456    5      0      0      0
</syntaxhighlight>
</syntaxhighlight>


{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
'''3. External device modifying media ports''':
|-
! colspan="2" style="background:#ffc107;" | Critical: Interface Packet Drops vs Sensor Drops
|-
| style="vertical-align: top;" | '''Interface drops (kernel level):'''
| Packets dropped by the network card driver BEFORE reaching VoIPmonitor. Use <code>ip -s -s l l</code> to check. Root cause is network infrastructure: switch overload, duplex mismatch, faulty NIC/switch port.
|-
| style="vertical-align: top;" | '''Sensor drops (VoIPmonitor level):'''
| Packets received by the OS but dropped by VoIPmonitor due to high CPU load, insufficient ringbuffer, or configuration limits. Check the "# packet drops" counter in GUI Settings → Sensors and <code>t0CPU</code> metric in logs.
|}
 
;Diagnosing Interface Packet Drops:
 
'''Step 1: Check if the dropped counter is increasing:'''
 
Run the interface statistics command multiple times while making test calls:


If SDP advertises one port but RTP arrives on different port (SBC/media server issue):
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# First measurement
# Compare SDP ports vs actual RTP
ip -s -s l l eth0 | grep -A 1 "RX:"
tshark -r call.pcap -Y "sip.Method == INVITE" -V | grep "m=audio"
 
tshark -r call.pcap -Y "rtp" -T fields -e udp.dstport | sort -u
# Make a test call during which you expect to see dropped packets
 
# Second measurement 10-30 seconds later
ip -s -s l l eth0 | grep -A 1 "RX:"
</syntaxhighlight>
</syntaxhighlight>


If the <code>dropped</code> value increases between measurements during test calls, the interface is losing packets due to infrastructure issues.
If ports don't match, the external device must be configured to preserve SDP ports - VoIPmonitor cannot compensate.
=== RTP Incorrectly Associated with Wrong Call (PBX Port Reuse) ===
'''Symptom''': RTP streams from one call appear associated with a different CDR when your PBX aggressively reuses the same IP:port across multiple calls.


'''Step 2: Identify the root cause of interface packet drops:'''
'''Cause''': When PBX reuses media ports, VoIPmonitor may incorrectly correlate RTP packets to the wrong call based on weaker correlation methods.


Common causes of network interface packet drops:
'''Solution''': Enable <code>rtp_check_both_sides_by_sdp</code> to require verification of both source and destination IP:port against SDP:
 
<syntaxhighlight lang="ini">
* '''Network switch port overload:''' The switch port connected to the VoIPmonitor sensor is receiving more traffic than it can forward to the sensor. This is common during peak traffic hours.
# voipmonitor.conf - require both source and destination to match SDP
* '''Duplex/speed mismatch:''' The server NIC and switch port are configured with mismatched speed or duplex settings (e.g., NIC set to 100Mbps/half-duplex while switch is 1Gbps/full-duplex).
rtp_check_both_sides_by_sdp = yes
* '''Faulty hardware:''' Defective network interface card (NIC) or a damaged switch port.
 
;Specific diagnostic actions:
 
* '''Check duplex/speed negotiation:'''
<syntaxhighlight lang="bash">
# Check the current speed and duplex setting
ethtool eth0
</syntaxhighlight>
Look for the <code>Speed</code> and <code>Duplex</code> values. Ensure they match the switch port configuration (e.g., Speed: 1000Mb/s, Duplex: Full).


* '''Check for driver errors:'''
# Alternative (strict) mode - allows initial unverified packets
<syntaxhighlight lang="bash">
rtp_check_both_sides_by_sdp = strict
# Look for NIC driver messages that indicate hardware issues
dmesg | grep -i eth0 | tail -50
</syntaxhighlight>
</syntaxhighlight>


* '''Test with a different network interface or cable:'''
{{Warning|Enabling this may prevent RTP association for calls using NAT, as the source IP:port will not match the SDP. Use <code>natalias</code> mappings or the <code>strict</code> setting to mitigate this.}}
If the issue persists after verifying duplex/speed, try connecting the sensor to a different switch port or using a different cable to rule out hardware faults.
=== Snaplen Truncation ===


;Step 3: Verify bidirectional SIP traffic in SPAN/mirroring configuration:
'''Symptom''': Large SIP messages truncated, incomplete headers.


Even if the interface shows no packet drops, verify that your network switch SPAN/mirror configuration is sending '''BOTH directions''' of SIP traffic to the sniffing interface. Missing one direction causes incomplete CDRs and incorrect Last Response tracking.
'''Solution''':
 
<syntaxhighlight lang="ini">
Use <code>tshark</code> during a test call to verify bidirectional SIP flow:
# voipmonitor.conf - increase packet capture size
 
snaplen = 8192
<syntaxhighlight lang="bash">
# Monitor INVITE requests and their responses to confirm bidirectional flow
# Replace eth0 with your sniffing interface
tshark -i eth0 -Y 'sip.CSeq.method == "INVITE" || sip.Status-Code' -n
</syntaxhighlight>
</syntaxhighlight>


If you see INVITE requests but NO corresponding responses (like 200 OK, 404, 500), your SPAN/mirror configuration is only capturing one direction of traffic. This requires network switch configuration changes:
For Kamailio siptrace, also check <code>trace_msg_fragment_size</code> in Kamailio config. See [[Sniffer_configuration#snaplen|snaplen documentation]].


* '''Cisco switches:''' Verify SPAN source includes <code>both</code> direction:
== PACKETBUFFER Saturation ==
  <syntaxhighlight lang="bash">
  show running-config | include monitor session
  # Should include: monitor session 1 source interface GigabitEthernet1/1 both
  </syntaxhighlight>


* '''Other switch vendors:''' Refer to switch documentation for SPAN mirroring direction configuration.
'''Symptom''': Log shows <code>PACKETBUFFER: memory is FULL</code>, truncated RTP recordings.


;Summary of workflow when interface packet drops are detected:
{{Warning|This alert refers to VoIPmonitor's '''internal packet buffer''' (<code>max_buffer_mem</code>), '''NOT system RAM'''. High system memory availability does not prevent this error. The root cause is always a downstream bottleneck (disk I/O or CPU) preventing packets from being processed fast enough.}}


# Use <code>ip -s -s l l</code> to check for increasing <code>dropped</code> counter
'''Before testing solutions''', gather diagnostic data:
# Confirm drops occur during test calls with repeated measurements
* Check sensor logs: <code>/var/log/syslog</code> (Debian/Ubuntu) or <code>/var/log/messages</code> (RHEL/CentOS)
# Check duplex/speed with <code>ethtool</code>
* Generate debug log via GUI: '''Tools → Generate debug log'''
# Verify switch port configuration matches NIC settings
# Check for hardware faults (different port, different cable)
# Verify SPAN/mirror sends both directions of SIP traffic with <code>tshark -Y sip.CSeq.method == "INVITE"</code>
# Resolve the underlying network infrastructure issue before tuning VoIPmonitor configuration


{{Warning|Interface packet drops cannot be fixed with VoIPmonitor configuration changes. Increasing ringbuffer, adjusting pcap_queue_deque_window_length, or other sniffer tuning will NOT resolve packet drops at the kernel/interface level. You must fix the network infrastructure first.}}
=== Diagnose: I/O vs CPU Bottleneck ===


;3B. Troubleshooting: Asymmetric Traffic Mirroring Across Multiple Interfaces or Hosts
{{Warning|Do not guess the bottleneck source. Use proper diagnostics first to identify whether the issue is disk I/O, CPU, or database-related. Disabling storage as a test is valid but should be used to '''confirm''' findings, not as the primary diagnostic method.}}


If SIP packets are visible on the network but CDRs are not appearing in the GUI, the issue may be that SIP requests and responses are being mirrored to '''different interfaces''' or '''different sniffer hosts''', rather than a single interface monitored by a single voipmonitor instance.
==== Step 1: Check IO[] Metrics (v2026.01.3+) ====


=== Diagnosis: Check Traffic on Each Interface and Host ===
'''Starting with version 2026.01.3''', VoIPmonitor includes built-in disk I/O monitoring that directly shows disk saturation status:


When investigating mirroring issues, you must verify packet flow on '''every network interface''' of '''each sniffer host'''. A common misconfiguration occurs when:
<syntaxhighlight lang="text">
 
[283.4/283.4Mb/s] IO[B1.1|L0.7|U45|C75|W125|R10|WI1.2k|RI0.5k]
* SIP requests (INVITE) are mirrored to interface A on sensor host 1
* SIP responses (200 OK) are mirrored to interface B on sensor host 1
* Or requests go to sensor host 1 and responses go to sensor host 2
 
This asymmetric mirroring prevents voipmonitor from correlating requests with responses, resulting in missing or incomplete CDRs.
 
=== Step 1: Identify All Sniffing Interfaces and Hosts ===
 
First, identify all interfaces configured for mirroring and all sensor hosts in your deployment:
 
<syntaxhighlight lang="bash">
# On each sniffer host, list all network interfaces
ip a | grep -E "^[0-9]+:|state UP"
 
# Check which interfaces voipmonitor is configured to use
grep "^interface" /etc/voipmonitor.conf
 
# Check for multiple voipmonitor instances running on the same host
ps aux | grep voipmonitor
</syntaxhighlight>
</syntaxhighlight>


=== Step 2: Capture Traffic on Each Interface Simultaneously ===
'''Quick interpretation:'''
{| class="wikitable"
|-
! Metric !! Meaning !! Problem Indicator
|-
| '''C''' (Capacity) || % of disk's sustainable throughput used || '''C ≥ 80% = Warning''', '''C ≥ 95% = Saturated'''
|-
| '''L''' (Latency) || Current write latency in ms || '''L ≥ 3× B''' (baseline) = Saturated
|-
| '''U''' (Utilization) || % time disk is busy || '''U > 90%''' = Disk at limit
|}


For each interface on each sniffer host, run a separate tcpdump capture during a test call:
'''If you see <code>DISK_SAT</code> or <code>WARN</code> after IO[]:'''
 
<syntaxhighlight lang="text">
<syntaxhighlight lang="bash">
IO[B1.1|L8.5|U98|C97|W890|R5|WI12.5k|RI0.1k] DISK_SAT
# On sensor host 1, interface eth0:
tcpdump -i eth0 -nn "sip" -w /tmp/sensor1_eth0.pcap &
 
# On sensor host 1, interface eth1 (if exists):
tcpdump -i eth1 -nn "sip" -w /tmp/sensor1_eth1.pcap &
 
# On sensor host 2, interface eth0:
tcpdump -i eth0 -nn "sip" -w /tmp/sensor2_eth0.pcap &
</syntaxhighlight>
 
Make a test call and stop the captures after 10-30 seconds.
 
=== Step 3: Analyze Captures to Detect Asymmetric Mirroring ===
 
Using tshark, check which interface received which part of the SIP dialog:
 
<syntaxhighlight lang="bash">
# Check capture 1 for INVITE requests
tshark -r /tmp/sensor1_eth0.pcap -Y "sip.CSeq.method == INVITE" -T fields -e sip.Call-ID
 
# Check capture 1 for SIP responses
tshark -r /tmp/sensor1_eth0.pcap -Y "sip.Status-Code" -T fields -e sip.Call-ID
 
# Check capture 2 for INVITE requests
tshark -r /tmp/sensor1_eth1.pcap -Y "sip.CSeq.method == INVITE" -T fields -e sip.Call-ID
 
# Check capture 2 for SIP responses
tshark -r /tmp/sensor1_eth1.pcap -Y "sip.Status-Code" -T fields -e sip.Call-ID
</syntaxhighlight>
</syntaxhighlight>


Compare the Call-IDs across captures. If you observe:
→ This confirms I/O bottleneck. Skip to [[#Solution:_I.2FO_Bottleneck|I/O Bottleneck Solutions]].


* INVITEs appear in capture 1, but responses for the same Call-ID appear only in capture 2
'''For older versions or additional confirmation''', continue with the steps below.
* Or INVITEs and responses are split across different hosts
* Or any combination where the complete SIP dialog is not on a single interface


Then your mirroring configuration is asymmetric.
{{Note|See [[Syslog_Status_Line#IO.5B....5D_-_Disk_I.2FO_Monitoring_.28v2026.01.3.2B.29|Syslog Status Line - IO[] section]] for detailed field descriptions.}}


=== Step 4: Count Packets Per Interface ===
==== Step 2: Read the Full Syslog Status Line ====


To quantify the asymmetry, count the SIP packets on each interface:
VoIPmonitor outputs a status line every 10 seconds. This is your first diagnostic tool:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Count total SIP packets on each interface
# Monitor in real-time
tshark -r /tmp/sensor1_eth0.pcap -Y "sip" | wc -l
journalctl -u voipmonitor -f
tshark -r /tmp/sensor1_eth1.pcap -Y "sip" | wc -l
# or
tshark -r /tmp/sensor2_eth0.pcap -Y "sip" | wc -l
tail -f /var/log/syslog | grep voipmonitor
</syntaxhighlight>
</syntaxhighlight>


If voipmonitor is running on only one interface but traffic is split across two, you will see partial SIP dialogs. The interface receiving only requests or only responses will not generate complete CDRs.
'''Example status line:'''
 
<syntaxhighlight lang="text">
=== Solution: Correct Mirroring Configuration for Symmetric Traffic Flow ===
calls[424] PS[C:4 S:41 R:13540] SQLq[C:0 M:0] heap[45|30|20] comp[48] [25.6Mb/s] t0CPU[85%] t1CPU[12%] t2CPU[8%] tacCPU[8|8|7|7%] RSS/VSZ[365|1640]MB
 
VoIPmonitor requires the '''complete SIP session (both requests and responses)''' to be mirrored to a '''SINGLE network interface''' monitored by a '''SINGLE voipmonitor sniffer instance'''.
 
==== Identify the Correct Source for Complete Mirroring ====
 
1. Determine which switch port(s), interface(s), or VLAN(s) carry the traffic you want to monitor
2. Trace the network path to understand where SIP requests and responses converge
3. Find a single point in your network where you can capture the bidirectional traffic
 
==== Configure SPAN/Mirror to Single Destination ====
 
Update your network switch's port mirroring (SPAN) configuration:
 
* Cisco switches example:
<syntaxhighlight lang="bash">
# Monitor both inbound and outbound traffic from source port
# Send complete session to a SINGLE destination port
monitor session 1 source interface GigabitEthernet1/1 both
monitor session 1 destination interface GigabitEthernet1/2
</syntaxhighlight>
</syntaxhighlight>


* Ensure the SPAN source uses the <code>both</code> keyword to capture bidirectional traffic
'''Key metrics for bottleneck identification:'''
* Ensure the SPAN destination is a single port connected to one voipmonitor sensor interface


==== Multi-Host Deployments ====
{| class="wikitable"
 
|-
If you must monitor traffic that is split across multiple network segments or hosts:
! Metric !! What It Indicates !! I/O Bottleneck Sign !! CPU Bottleneck Sign
 
1. Use VoIPmonitor's '''Client-Server''' mode (distributed architecture) instead of multiple independent sniffers
2. Configure remote probes to forward all packets to one central analysis server
3. See [[Sniffer_distributed_architecture|Distributed Architecture: Client-Server Mode]] for setup details
 
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
|-
! colspan="2" style="background:#ffc107;" | Asymmetric Mirroring Prevention Best Practices
| <code>heap[A&#124;B&#124;C]</code> || Buffer fill % (primary / secondary / processing) || High A with low t0CPU || High A with high t0CPU
|-
|-
| style="vertical-align: top;" | '''Single Interface Rule:'''
| <code>t0CPU[X%]</code> || Packet capture thread (single-core, cannot parallelize) || Low (<50%) || High (>80%)
| Always ensure complete SIP sessions (requests + responses) go to one monitored interface on one sensor instance.
|-
|-
| style="vertical-align: top;" | '''Verification Method:'''
| <code>comp[X]</code> || Active compression threads || Very high (maxed out) || Normal
| During installation, use tshark on the target interface to verify INVITEs AND responses have matching Call-IDs.
|-
|-
| style="vertical-align: top;" | '''Switch SPAN Configuration:'''
| <code>SQLq[C:X M:Y]</code> || Pending SQL queries || Growing = database bottleneck || Stable
| Use <code>both</code> direction in SPAN/mirror commands. Verify no duplicate or split destination ports.
|-
|-
| style="vertical-align: top;" | '''Avoid Multiple Sniffers:'''
| <code>tacCPU[...]</code> || TAR compression threads || All near 100% = compression bottleneck || Normal
| Do not run multiple independent voipmonitor instances on different interfaces unless using Client-Server mode with packet forwarding.
|}
|}


=== Step 5: Verify Fix After Mirroring Changes ===
'''Interpretation flowchart:'''


After correcting the network mirroring configuration:
<kroki lang="mermaid">
graph TD
    A[heap values rising] --> B{Check t0CPU}
    B -->|t0CPU > 80%| C[CPU Bottleneck]
    B -->|t0CPU < 50%| D{Check comp and tacCPU}
    D -->|comp maxed, tacCPU high| E[I/O Bottleneck<br/>Disk cannot keep up with writes]
    D -->|comp normal| F{Check SQLq}
    F -->|SQLq growing| G[Database Bottleneck]
    F -->|SQLq stable| H[Mixed/Other Issue]


1. Restart the voipmonitor service: <code>systemctl restart voipmonitor</code>
    C --> C1[Solution: CPU optimization]
2. Run a test call
    E --> E1[Solution: Faster storage]
3. Verify CDRs appear in the GUI within 30-60 seconds
    G --> G1[Solution: MySQL tuning]
4. Open the CDR and confirm it shows complete SIP history (INVITE + responses)
</kroki>
5. If using tcpdump for verification, confirm the complete dialog is now on one interface:


<syntaxhighlight lang="bash">
==== Step 3: Linux I/O Diagnostics ====
# Should now show both INVITEs and responses with same Call-IDs
tshark -i eth0 -Y "sip" -T fields -e sip.Call-ID -e sip.Method -e sip.Status-Code | head -20
</syntaxhighlight>


;3. Check for Promiscuous Mode (for SPAN/RSPAN Mirrored Traffic):
Use these standard Linux tools to confirm I/O bottleneck:
'''Important:''' Promiscuous mode requirements depend on your traffic mirroring method:


* '''SPAN/RSPAN (Layer 2 mirroring):''' The network interface '''must''' be in promiscuous mode. Mirrored packets retain their original MAC addresses, so the interface would normally ignore them. Promiscuous mode forces the interface to accept all packets regardless of destination MAC.
'''Install required tools:'''
<syntaxhighlight lang="bash">
# Debian/Ubuntu
apt install sysstat iotop ioping


* '''ERSPAN/GRE/TZSP/VXLAN (Layer 3 tunnels):''' Promiscuous mode is '''NOT required'''. These tunneling protocols encapsulate the mirrored traffic inside IP packets that are addressed directly to the sensor's IP address. The operating system receives these packets normally, and VoIPmonitor automatically decapsulates them to extract the inner SIP/RTP traffic.
# CentOS/RHEL
 
yum install sysstat iotop ioping
For SPAN/RSPAN deployments, check the current promiscuous mode status:
<syntaxhighlight lang="bash">
ip link show eth0
</syntaxhighlight>
</syntaxhighlight>
Look for the <code>PROMISC</code> flag.


Enable promiscuous mode manually if needed:
'''2a) iostat - Disk utilization and wait times'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
ip link set eth0 promisc on
# Run for 10 intervals of 2 seconds
iostat -xz 2 10
</syntaxhighlight>
</syntaxhighlight>
If this solves the problem, you should make the change permanent. The <code>install-script.sh</code> for the sensor usually attempts to do this, but it can fail.


;3A. Troubleshooting: Missing Packets for Specific IPs During High-Traffic Periods:
'''Key output columns:'''
If calls are missing only for certain IP addresses or specific call flows (particularly during high-traffic periods), the issue is typically at the network infrastructure level (SPAN configuration) rather than sensor resource limits. Use this systematic approach:
<syntaxhighlight lang="text">
 
Device  r/s    w/s  rkB/s  wkB/s  await  %util
=== Step 1: Use tcpdump to Verify Packet Arrival ===
sda    12.50  245.30  50.00  1962.40  45.23  98.50
 
Before tuning any sensor configuration, first verify if the missing packets are actually reaching the sensor's network interface. Use <code>tcpdump</code> for this verification:
 
<syntaxhighlight lang="bash">
# Listen for SIP packets from a specific IP during the next high-traffic window
# Replace eth0 with your interface and 10.1.2.3 with the problematic IP
tcpdump -i eth0 -nn "host 10.1.2.3 and port 5060" -v
 
# Or capture to a file for later analysis
tcpdump -i eth0 -nn "host 10.1.2.3 and port 5060" -w /tmp/trace_10.1.2.3.pcap
</syntaxhighlight>
</syntaxhighlight>


Interpret the results:
{| class="wikitable"
* '''If you see SIP packets arriving:''' The traffic reaches the sensor. The issue is likely a sensor resource bottleneck (CPU, memory, or configuration limits). Proceed to [[#Sensor_Resource_Bottlenecks|Step 4: Check Sensor Statistics]].
* '''If you see NO packets or only intermittent packets:''' The traffic is not reaching the sensor. This indicates a network infrastructure issue. Proceed to [[#SPAN_Configuration_Troubleshooting|Step 2: Check SPAN Configuration]].
 
=== Step 2: Check SPAN Configuration for Bidirectional Capture ===
 
If packets are missing at the interface level, verify your network switch's SPAN (port mirroring) configuration. During high-traffic periods, switches may have insufficient SPAN buffer capacity, causing packets to be dropped in the mirroring process itself.
 
Key verification points:
 
* '''Verify Source Ports:''' Confirm that both source IP addresses (or the switch ports they connect to) are included in the SPAN source list. Missing one direction of the call flow will result in incomplete CDRs.
 
* '''Check for Bidirectional Mirroring:''' Your SPAN configuration must capture '''BOTH inbound and outbound traffic'''. On most Cisco switches, this requires specifying:
  <syntaxhighlight lang="bash">
  monitor session 1 source interface GigabitEthernet1/1 both
  </syntaxhighlight>
 
  Replace <code>both</code> with:
  * <code>rx</code> for incoming traffic only
  * <code>tx</code> for outgoing traffic only
  * <code>both</code> for bidirectional capture (recommended)
 
* '''Verify Destination Port:''' Confirm the SPAN destination points to the switch port where the VoIPmonitor sensor is connected.
 
* '''Check SPAN Buffer Saturation (High-Traffic Issues):''' Some switches have limited SPAN buffer capacity. When monitoring multiple high-traffic ports simultaneously, the SPAN buffer may overflow during peak usage, causing randomized packet drops. Symptoms:
  ** Drops occur only during busy hours
  ** Missing packets are inconsistent across different calls
  ** Sensor CPU usage and t0CPU metrics appear normal (no bottleneck at sensor)
 
  Solutions:
  ** Reduce the number of monitored source ports in the SPAN session
  ** Use multiple SPAN sessions if your switch supports it
  ** Consider upgrading to a switch with higher SPAN buffer capacity
 
* '''Verify Switch Interface Counters for Packet Drops:''' Check the network switch interface counters to determine if the switch itself is dropping packets during the mirroring process. This is critical when investigating false low MOS scores or packet loss reports.
 
  Cisco switches:
  <syntaxhighlight lang="bash">
  # Show general interface statistics for the SPAN source port
  show interface GigabitEthernet1/1 counters
  show interface GigabitEthernet1/1 | include drops|errors|Input queue|Output queue
 
  # Show detailed interface status (look for input errors, CRC, frame)
  show interface GigabitEthernet1/1 detail
 
  # Monitor in real-time during a high-traffic period
  show interface Gi1/1 accounting
  </syntaxhighlight>
 
  Key indicators of switch-level packet loss:
  ** Non-zero input errors or CRC errors on source/destination ports
  ** Input queue drops (indicating switch buffer overflow)
  ** Increasing drop counters during peak traffic hours
  ** Output errors on the SPAN destination port (sensor may not be accepting fast enough)
 
  If switch interface counters show drops, the issue is at the network infrastructure level (overloaded switch), not the VoIPmonitor sensor. Consult your network administrator for switch optimization or consider redistributing SPAN traffic across multiple ports.
 
* '''Verify VLAN Trunking:''' If the monitored traffic spans different VLANs, ensure the SPAN destination port is configured as a trunk to carry all necessary VLAN tags. Without trunk mode, packets from non-native VLANs will be dropped or stripped of their tags.
 
For detailed instructions on configuring SPAN/ERSPAN/GRE for different network environments, see [[Sniffing_modes]].
 
=== Step 2A: EtherChannel/LACP Bonded Interface Configuration ===
 
If your network uses Ethernet channel bonding (EtherChannel, LACP, port-channel, bonding, teaming), VoIPmonitor may report false positive packet loss and lower MOS scores even when actual loss is minimal. This occurs when VoIPmonitor is configured to monitor a bridged/bonded interface (e.g., `br0`, `bond0`, `team0`) instead of monitoring the individual physical interfaces that carry the actual traffic.
 
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
|-
! colspan="2" style="background:#ffc107;" | Issue: False Packet Loss on Bonded Interfaces
! Column !! Description !! Problem Indicator
|-
|-
| style="vertical-align: top;" | '''Symptoms:'''
| <code>%util</code> || Device utilization percentage || '''> 90%''' = disk saturated
| VoIPmonitor reports packet loss and low MOS scores, but network devices show minimal or no actual loss. RTP processing threads appear overloaded. Switch SPAN configuration is correct but packets still show as missing.
|-
|-
| style="vertical-align: top;" | '''Root Cause:'''
| <code>await</code> || Average I/O wait time (ms) || '''> 20ms''' for SSD, '''> 50ms''' for HDD = high latency
| When monitoring a bonded interface (e.g., `br0` for an EtherChannel bundle), VoIPmonitor cannot correctly track RTP streams because packets from the same SIP call may be distributed across multiple physical interfaces by the bonding driver. This causes packet association failures and "false" loss detection.
|-
|-
| style="vertical-align: top;" | '''Solution:'''
| <code>w/s</code> || Writes per second || Compare with disk's rated IOPS
| Configure <code>interface</code> to use a comma-separated list of the individual physical interfaces that make up the EtherChannel bundle, not the bonded interface itself.
|}
|}


;Identify Bonded Interface Misconfiguration:
'''2b) iotop - Per-process I/O usage'''
 
Check if VoIPmonitor is configured to monitor a bonded/bundled interface:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check current interface setting
# Show I/O by process (run as root)
grep "^interface" /etc/voipmonitor.conf
iotop -o
 
# Common problematic values that indicate bonded interfaces:
# interface = br0        (bridge interface)
# interface = bond0      (Linux bonding)
# interface = team0      (NetworkManager teaming)
# interface = port-channel1 (Cisco/Nexus EtherChannel)
</syntaxhighlight>
</syntaxhighlight>


;Solution: Use Individual Physical Interfaces:
Look for <code>voipmonitor</code> or <code>mysqld</code> dominating I/O. If voipmonitor shows high DISK WRITE but system <code>%util</code> is 100%, disk cannot keep up.
 
Edit <code>/etc/voipmonitor.conf</code> and change the <code>interface</code> setting to use the individual physical interfaces that comprise the EtherChannel bundle:


'''2c) ioping - Quick latency check'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Example: EtherChannel with ports p3p1 and p3p2 bundled into br0
# Test latency on VoIPmonitor spool directory
# BEFORE (INCORRECT):
cd /var/spool/voipmonitor
# interface = br0
ioping -c 20 .
 
# AFTER (CORRECT):
interface = p3p1,p3p2
</syntaxhighlight>
</syntaxhighlight>


The comma-separated list allows VoIPmonitor to create a dedicated capture thread for each physical interface, ensuring proper RTP stream association across the EtherChannel bundle.
'''Expected results:'''
 
{| class="wikitable"
;Verify Physical Interface Names:
|-
 
! Storage Type !! Healthy Latency !! Problem Indicator
To identify the correct physical interface names for your EtherChannel setup:
<syntaxhighlight lang="bash">
# List all network interfaces
ip link show
 
# Check which interfaces are part of the bond/team
cat /proc/net/bonding/bond0      # for Linux bonding
teamdctl team0 state dump        # for NetworkManager teaming
 
# Or check switch configuration for port-channel members
# Example: Cisco switch output
# show etherchannel summary
# shows: Port-channel1 (Po1) = eth0, eth1, eth2, eth3
</syntaxhighlight>
 
;After Making Configuration Changes:
 
Restart the VoIPmonitor service for changes to take effect:
<syntaxhighlight lang="bash">systemctl restart voipmonitor</syntaxhighlight>
 
Then verify that packet loss reporting has improved and RTP processing threads are no longer overloaded.
 
;Related Issues:
 
* '''Packet Reordering in EtherChannel:''' Even with correct physical interface monitoring, EtherChannel distributes packets across multiple links using a hashing algorithm. This can cause packets in the same RTP stream to arrive out of order (packet delay variation). High jitter/variation may still cause reduced MOS F1 scores. Compare MOS F1 (50ms buffer) vs MOS F2 (200ms buffer) - if F2 is significantly higher, the issue is jitter/reordering, not actual loss.
 
* '''SPAN Bandwidth for Aggregated Links:''' When monitoring EtherChannel bundles, ensure the SPAN destination port has sufficient bandwidth. For example, if you have 4x1Gbps EtherChannel (4Gbps total) but monitor to a 1Gbps SPAN port, the switch will drop packets at the SPAN destination. Always use a SPAN port speed equal to or greater than the sum of the EtherChannel bandwidth.
 
=== Step 3: Check for UDP Fragmentation Issues ===
 
When investigating missing packets, especially for SIP over UDP, a common issue is packet fragmentation. If the MTU path between systems causes SIP packets to be fragmented (typically >1480 bytes), the IP fragments will not contain UDP port information, making port-based tcpdump filters miss these fragments.
 
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
|-
! colspan="2" style="background:#ffc107;" | Critical: Check Defragmentation Settings FIRST
| NVMe SSD || < 0.5 ms || > 2 ms
|-
|-
| style="vertical-align: top;" | '''Before using tcpdump:'''
| SATA SSD || < 1 ms || > 5 ms
| Verify VoIPmonitor's defragmentation is enabled in <code>/etc/voipmonitor.conf</code>. If these are disabled, VoIPmonitor cannot reassemble IP fragments before parsing SIP, causing missing packets even when traffic reaches the interface correctly.
|-
|-
| style="vertical-align: top;" | '''Required settings:'''
| HDD (7200 RPM) || < 10 ms || > 30 ms
| <code>udpfrag = yes</code> (default) for UDP fragment reassembly<br/><code>sip_tcp_reassembly_ext = yes</code> (default) for TCP reassembly
|}
|}
;Step 1: Verify defragmentation is enabled:


Check your VoIPmonitor configuration:
==== Step 4: Linux CPU Diagnostics ====
<syntaxhighlight lang="bash">
# Check if UDP fragment reassembly is enabled
grep "^udpfrag" /etc/voipmonitor.conf


# Check if TCP reassembly is enabled
'''3a) top - Overall CPU usage'''
grep "^sip_tcp_reassembly_ext" /etc/voipmonitor.conf
</syntaxhighlight>
 
Both should be set to <code>yes</code> (these are the defaults). If either is set to <code>no</code>, VoIPmonitor will not reassemble fragmented packets, causing packets larger than the MTU to be ignored or parsed incorrectly.
 
If the settings are correct and you are still experiencing issues, proceed to the following diagnostic steps using tcpdump.
 
;Step 2: Identify if fragmentation may be causing packet loss:
If you are investigating missing INVITE packets (especially those with large SDP), check if packet fragmentation is in the network path. Large SIP packets get fragmented at IP layers, and subsequent fragments only contain IP headers (no UDP port information).
 
;Step 3: Do NOT use port-based filters when investigating fragmentation:
<code>tcpdump</code> or <code>tshark</code> filters based on UDP port will miss IP fragments, because fragments only contain the IP header (no transport layer port information). Instead, filter by IP address.
 
;Step 4: Use IP-based tcpdump filters for fragmented packets:
When capturing to investigate missing packets that may be fragmented, filter by IP addresses instead of ports:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# CORRECT: Filter by IP address to capture fragments
# Press '1' to show per-core CPU
# Replace opensips_ip and carrier_ip with actual IP addresses
top
tcpdump -i eth0 -nn "host opensips_ip and carrier_ip" -w /tmp/fragmentation_test.pcap
 
# INCORRECT: Port filter will miss IP fragments
tcpdump -i eth0 -nn "host opensips_ip and port 5060" -w /tmp/fragmentation_test.pcap
</syntaxhighlight>
</syntaxhighlight>


;Step 5: Test with a specific call that is missing from the GUI:
Look for:
Make a test call that exhibits the missing packet issue, and capture the entire traffic flow between the two endpoints:
* Individual CPU core at 100% (t0 thread is single-threaded)
<syntaxhighlight lang="bash">
* High <code>%wa</code> (I/O wait) vs high <code>%us/%sy</code> (CPU-bound)
# Capture all traffic between two IPs during a test call
# Replace with your actual IP addresses
tcpdump -i eth0 -nn "host 192.168.1.100 and 203.0.113.50" -w /tmp/test_call_capture.pcap
</syntaxhighlight>


;Step 6: Analyze the capture for fragmentation:
'''3b) Verify voipmonitor threads'''
Open the pcap file in <code>tshark</code> or Wireshark to check for fragmented IP packets:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Look for fragmented IP packets in the capture
# Show voipmonitor threads with CPU usage
tshark -r /tmp/test_call_capture.pcap -Y "ip.fragments"
top -H -p $(pgrep voipmonitor)
 
# Count fragments
tshark -r /tmp/test_call_capture.pcap -Y "ip.fragments" | wc -l
</syntaxhighlight>
</syntaxhighlight>


If you see fragmented packets, especially for large SIP INVITE messages, this confirms that port-based filters would miss fragments, which explains why the call appears incomplete in VoIPmonitor.
If one thread shows ~100% CPU while others are low, you have a CPU bottleneck on the capture thread (t0).


;{{Note|If tcpdump with IP-based filters captures the missing packets while VoIPmonitor does not see them, share the pcap file and your <code>voipmonitor.conf</code> with VoIPmonitor support for further analysis.}}
==== Step 5: Decision Matrix ====


=== Step 3A: Check for Sensor Resource Bottlenecks ===
{| class="wikitable"
|-
! Observation !! Likely Cause !! Go To
|-
| <code>heap</code> high, <code>t0CPU</code> > 80%, iostat <code>%util</code> low || '''CPU Bottleneck''' || [[#Solution: CPU Bottleneck|CPU Solution]]
|-
| <code>heap</code> high, <code>t0CPU</code> < 50%, iostat <code>%util</code> > 90% || '''I/O Bottleneck''' || [[#Solution: I/O Bottleneck|I/O Solution]]
|-
| <code>heap</code> high, <code>t0CPU</code> < 50%, iostat <code>%util</code> < 50%, <code>SQLq</code> growing || '''Database Bottleneck''' || [[#SQL Queue Overload|Database Solution]]
|-
| <code>heap</code> normal, <code>comp</code> maxed, <code>tacCPU</code> all ~100% || '''Compression Bottleneck''' (type of I/O) || [[#Solution: I/O Bottleneck|I/O Solution]]
|}


If <code>tcpdump</code> confirms that packets are arriving at the interface consistently, but VoIPmonitor is still missing them, the issue may be sensor resource limitations.
==== Step 6: Confirmation Test (Optional) ====


* '''Check Packet Drops:''' In the GUI, navigate to '''Settings → Sensors''' and look at the "# packet drops" counter. If this counter is non-zero or increasing during high traffic:
After identifying the likely cause with the tools above, you can confirm with a storage disable test:
  ** Increase the <code>ringbuffer</code> size in <code>voipmonitor.conf</code> (default 50 MB, max 2000 MB)
  ** Check the <code>t0CPU</code> metric in system logs - if consistently above 90%, you may need to upgrade CPU or optimize NIC drivers


* '''Monitor Memory Usage:''' Check for OOM (Out of Memory) killer events:
<syntaxhighlight lang="ini">
  <syntaxhighlight lang="bash">
# /etc/voipmonitor.conf - temporarily disable all storage
  grep -i "out of memory\|killed process" /var/log/syslog | tail -20
savesip = no
  </syntaxhighlight>
savertp = no
 
savertcp = no
* '''SIP Packet Limits:''' If only long or chatty calls are affected, check the <code>max_sip_packets_in_call</code> and <code>max_invite_packets_in_call</code> limits in <code>voipmonitor.conf</code>.
savegraph = no
 
;3. Verify Your SPAN/Mirror/TAP Configuration:
This is the most common cause of no traffic. Double-check your network switch or hardware tap configuration to ensure:
* The correct source ports (where your PBX/SBC is connected) are being monitored.
* The correct destination port (where your VoIPmonitor sensor is connected) is configured.
* If you are monitoring traffic across different VLANs, ensure your mirror port is configured to carry all necessary VLAN tags (often called "trunk" mode).
 
;4. Investigate Packet Encapsulation (If tcpdump shows traffic but VoIPmonitor does not):
If <code>tcpdump</code> or <code>tshark</code> shows packets reaching the interface but VoIPmonitor is not capturing them, the traffic may be encapsulated in a tunnel that VoIPmonitor cannot automatically process without additional configuration. Common encapsulations include VLAN tags, ERSPAN, GRE, VXLAN, and TZSP.
 
First, capture a sample of the traffic for analysis:
<syntaxhighlight lang="bash">
# Capture 100 packets of SIP traffic to a pcap file
tcpdump -i eth0 -c 100 -s0 port 5060 -w /tmp/encapsulation_check.pcap
</syntaxhighlight>
</syntaxhighlight>


Then analyze the capture to identify encapsulation:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check for VLAN-tagged packets (802.1Q)
systemctl restart voipmonitor
tshark -r /tmp/encapsulation_check.pcap -Y "vlan"
# Monitor for 5-10 minutes during peak traffic
 
journalctl -u voipmonitor -f | grep heap
# Check for GRE tunnels
tshark -r /tmp/encapsulation_check.pcap -Y "gre"
 
# Check for ERSPAN (GRE encapsulated with ERSPAN protocol)
tshark -r /tmp/encapsulation_check.pcap -Y "gre && ip.proto == 47"
 
# Check for VXLAN (UDP port 4789)
tshark -r /tmp/encapsulation_check.pcap -Y "udp.port == 4789"
 
# Check for TZSP (UDP ports 37008 or 37009)
tshark -r /tmp/encapsulation_check.pcap -Y "udp.port == 37008 || udp.port == 37009"
 
# Show packet summary to identify any unusual protocol stacks
tshark -r /tmp/encapsulation_check.pcap -V | head -50
</syntaxhighlight>
 
Identifying encapsulation issues:
* '''VLAN tags present:''' Ensure VoIPmonitor's <code>sipport</code> filter does not use <code>udp</code> (which may drop VLAN-tagged packets). Comment out the <code>filter</code> directive in <code>voipmonitor.conf</code> to test.
 
* '''ERSPAN/GRE tunnels:''' Promiscuous mode is NOT required for these Layer 3 tunnels. Verify that tunneling is configured correctly on your network device and that the packets are addressed to the sensor's IP. VoIPmonitor automatically decapsulates ERSPAN and GRE.
 
* '''VXLAN/TZSP tunnels:''' These specialized tunneling protocols require proper configuration on the sending device. Consult your network device documentation for VoIPmonitor compatibility requirements.
 
If encapsulation is identified as the issue, review [[Sniffing_modes]] for detailed configuration guidance.
 
;3B. Troubleshooting: RTP Streams Not Displayed for Specific Provider:
If SIP signaling appears correctly in the GUI for calls from a specific provider, but RTP streams (audio quality graphs, waveform visualization) are missing for that provider while working correctly for other call paths, use this systematic approach to identify the cause.
 
=== Step 1: Make a Test Call to Reproduce the Issue===
 
First, create a controlled test scenario to investigate the specific provider.
 
* Determine if the issue affects ALL calls from this provider or only some (e.g., specific codecs, call duration, time of day)
* Make a test call that reproduces the problem (e.g., from the problematic provider to a test number)
* Allow the call to establish and run for at least 30-60 seconds to capture meaningful RTP data
 
=== Step 2: Capture Packets on the Sniffing Interface During the Test Call ===
 
During the test call, use <code>tcpdump</code> (or <code>tshark</code>) to directly capture packets on the network interface configured in <code>voipmonitor.conf</code>. This tells you whether RTP packets are being received by the sensor.
 
<syntaxhighlight lang="bash">
# Capture SIP and RTP packets from the specific provider IP during your test call
# Replace eth0 with your interface and 1.2.3.4 with the provider's IP
sudo tcpdump -i eth0 -nn "host 1.2.3.4 and (udp port 5060 or (udp[0] & 0x78) == 0x78)" -v
 
# Capture RTP to a file for detailed analysis (recommended)
sudo tcpdump -i eth0 -nn "host 1.2.3.4 and rtp" -w /tmp/test_provider_rtp.pcap
</syntaxhighlight>
</syntaxhighlight>


Note: The RTP filter <code>(udp[0] & 0x78) == 0x78</code> matches packets with the first two bits of the first byte set to "10", which is characteristic of RTP.
* If <code>heap</code> values drop to near zero → confirms '''I/O bottleneck'''
* If <code>heap</code> values remain high → confirms '''CPU bottleneck'''


=== Step 3: Compare Raw Packet Capture with Sensor Output ===
{{Warning|Remember to re-enable storage after testing! This test causes call recordings to be lost.}}


After the test call:
=== Solution: I/O Bottleneck ===


* Check what tcpdump captured:
{{Note|If you see <code>IO[...] DISK_SAT</code> or <code>WARN</code> in the syslog status line (v2026.01.3+), disk saturation is already confirmed. See [[Syslog_Status_Line#IO.5B....5D_-_Disk_I.2FO_Monitoring_.28v2026.01.3.2B.29|IO[] Metrics]] for details.}}
<syntaxhighlight lang="bash">
# Count SIP packets
tshark -r /tmp/test_provider_rtp.pcap -Y "sip" | wc -l
 
# Count RTP packets
tshark -r /tmp/test_provider_rtp.pcap -Y "rtp" | wc -l
 
# View RTP stream details
tshark -r /tmp/test_provider_rtp.pcap -Y "rtp" -T fields -e rtp.ssrc -e rtp.seq -e rtp.ptype -e udp.srcport -e udp.dstport | head -20
</syntaxhighlight>


* Check what VoIPmonitor recorded:
'''Quick confirmation (for older versions):'''
  * Open the CDR for your test call in the GUI
  * Verify if the "Received Packets" column shows non-zero values for the provider leg
  * Check if the "Streams" section shows RTP quality graphs and waveform visualization


* Compare the results:
Temporarily save only RTP headers to reduce disk write load:
** '''If tcpdump shows NO RTP packets:''' The RTP traffic is not reaching the sensor interface. This indicates a network-level issue (asymmetric routing, SPAN configuration missing the RTP path, or firewall). You need to troubleshoot the network infrastructure, not VoIPmonitor.
 
** '''If tcpdump shows RTP packets but the GUI shows no streams or zero received packets:''' The packets are reaching the sensor but VoIPmonitor is not processing them. Check:
* [[#Check_GUI_Capture_Rules_(Causing_Call_Stops)|Step 5: Check GUI Capture Rules]] - Look for capture rules targeting the provider's IP with RTP set to "DISCARD" or "Header Only"
* [[Tls|TLS/SSL Decryption]] - Verify SRTP decryption is configured correctly if the provider uses encryption
* [[Sniffer_configuration]] - Check for any problematic <code>sipport</code> or <code>filter</code> settings
 
For more information on capture rules that affect RTP storage, see [[Capture_rules]].
 
;5. Check for Non-Call SIP Traffic Only:
If you see SIP traffic but it consists only of OPTIONS, NOTIFY, SUBSCRIBE, or MESSAGE methods (without any INVITE packets), there are no calls to generate CDRs. This can occur in environments that use SIP for non-call purposes like heartbeat checks or instant messaging.
 
You can configure VoIPmonitor to process and store these non-call SIP messages. See [[SIP_OPTIONS/SUBSCRIBE/NOTIFY]] and [[MESSAGES]] for configuration details.
 
Enable non-call SIP message processing in '''/etc/voipmonitor.conf''':
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Process SIP OPTIONS (qualify pings). Default: no
# /etc/voipmonitor.conf
sip-options = yes
savertp = header
 
# Process SIP MESSAGE (instant messaging). Default: yes
sip-message = yes
 
# Process SIP SUBSCRIBE requests. Default: no
sip-subscribe = yes
 
# Process SIP NOTIFY requests. Default: no
sip-notify = yes
</syntaxhighlight>
</syntaxhighlight>


Note that enabling these for processing and storage can significantly increase database load in high-traffic scenarios. Use with caution and monitor SQL queue growth. See [[SIP_OPTIONS/SUBSCRIBE/NOTIFY#Performance_Tuning|Performance Tuning]] for optimization tips.
Restart the sniffer and monitor. If heap usage stabilizes and "MEMORY IS FULL" errors stop, the issue is confirmed to be storage I/O.
 
== Step 4: Check the VoIPmonitor Configuration ==
If <code>tshark</code> sees traffic but VoIPmonitor does not, the problem is almost certainly in <code>voipmonitor.conf</code>.
 
;1. Check the <code>interface</code> directive:
Make sure the <code>interface</code> parameter in <code>/etc/voipmonitor.conf</code> exactly matches the interface where you see traffic with <code>tshark</code>. For example: <code>interface = eth0</code>.
 
=== Troubleshooting: Wrong Interface Name ===


If the <code>interface</code> directive is set to an interface name that does not exist on the system, the sensor will fail to capture traffic completely. This is a common issue when network interface names change after system updates or hardware reconfiguration.
'''Check storage health before upgrading:'''
 
;Step 1: Identify the correct interface name:
Use either of these commands to list all available network interfaces:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Option 1: Modern Linux systems
# Check drive health
ip a
smartctl -a /dev/sda


# Option 2: Older systems
# Check for I/O errors in system logs
ifconfig
dmesg | grep -i "i/o error\|sd.*error\|ata.*error"
</syntaxhighlight>
</syntaxhighlight>


Look for the interface that is receiving traffic. Common interface names include:
Look for reallocated sectors, pending sectors, or I/O errors. Replace failing drives before considering upgrades.
* <code>eth0, eth1, eth2...</code> (classic Ethernet naming)
* <code>ens33, ens34, enp0s3...</code> (predictable naming on modern systems)
* <code>enp2s0f0, enp2s0f1...</code> (multi-port NICs)


;Step 2: Verify the interface exists and is UP:
'''Storage controller cache settings:'''
<syntaxhighlight lang="bash">
{| class="wikitable"
# Check specific interface status (replace eth0 with your interface name)
|-
ip link show eth0
! Storage Type !! Recommended Cache Mode
|-
| HDD / NAS || WriteBack (requires battery-backed cache)
|-
| SSD || WriteThrough (or WriteBack with power loss protection)
|}


# The output should show "UP" and "LOWER_UP" to indicate the interface is active
Use vendor-specific tools to configure cache policy (<code>megacli</code>, <code>ssacli</code>, <code>perccli</code>).
</syntaxhighlight>


;Step 3: Update <code>/etc/voipmonitor.conf</code>:
'''Storage upgrades (in order of effectiveness):'''
Edit the <code>interface</code> directive to use the correct interface name:
{| class="wikitable"
<syntaxhighlight lang="ini">
|-
# /etc/voipmonitor.conf
! Solution !! IOPS Improvement !! Notes
interface = ens33
|-
</syntaxhighlight>
| '''NVMe SSD''' || 50-100x vs HDD || Best option, handles 10,000+ concurrent calls
 
;Step 4: Restart the VoIPmonitor service:
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
systemctl status voipmonitor
</syntaxhighlight>
 
Verify the service shows <code>Active: active (running)</code> after the restart.
 
;2. Check the <code>sipport</code> directive:
By default, VoIPmonitor only listens on port 5060. If your PBX uses a different port for SIP, you must add it. '''Common causes of missing calls:'''
* '''Missing ports:''' Some providers use alternate SIP ports (5061, 5080, etc.). If these are not listed, calls on those ports will be ignored.
* '''Syntax errors:''' List multiple ports comma-separated without extra commas or trailing characters. Correct syntax: <code>sipport = 5060,5061</code> or <code>sipport = 5060,5080</code>
* '''Ranges:''' You can specify port ranges using dashes: <code>sipport = 5060,5070-5080</code>
Example:
<code>sipport = 5060,5080</code>
 
;3. '''Distributed/Probe Setup Considerations:'''
If you are using a remote sensor (probe) with Packet Mirroring (<code>packetbuffer_sender=yes</code>), call detection depends on configuration on '''both''' the probe and the central analysis host.
 
Common symptom: The probe captures traffic (visible via <code>tcpdump</code>), but the central server records incomplete or missing CDRs for calls on non-default ports.
 
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
|-
! colspan="2" style="background:#ffc107;" | Critical: Both Systems Must Have Matching sipport Configuration
| '''SATA SSD''' || 20-50x vs HDD || Good option, handles 5,000+ concurrent calls
|-
|-
| style="vertical-align: top;" | '''Probe side:'''
| '''RAID 10 with BBU''' || 5-10x vs single disk || Enable WriteBack cache (requires battery backup)
| The probe captures packets from the network interface. Its <code>sipport</code> setting determines which UDP ports it considers as SIP traffic to capture and forward.
|-
|-
| style="vertical-align: top;" | '''Central server side:'''
| '''Separate storage server''' || Variable || Use [[Sniffer_distributed_architecture|client/server mode]]
| When receiving raw packets in Packet Mirroring mode, the central server analyzes the packets locally. Its <code>sipport</code> setting determines which ports it interprets as SIP during analysis. If a port is missing here, packets are captured but not recognized as SIP, resulting in missing CDRs.
|}
|}


:'''Troubleshooting steps for distributed probe setups:'''
'''Filesystem tuning (ext4):'''
 
::1. Verify traffic reachability on the probe:
::Use <code>tcpdump</code> on the probe VM to confirm SIP packets for the missing calls are arriving on the expected ports.
::<syntaxhighlight lang="bash">
# On the probe VM
tcpdump -i eth0 -n port 5061
</syntaxhighlight>
 
::2. Check the probe's ''voipmonitor.conf'':
::Ensure the <code>sipport</code> directive on the probe includes all necessary SIP ports used in your network.
::<syntaxhighlight lang="ini">
# /etc/voipmonitor.conf on the PROBE
sipport = 5060,5061,5080,6060
</syntaxhighlight>
 
::3. Check the central analysis host's ''voipmonitor.conf'':
::'''This is the most common cause of missing calls in distributed setups.''' The central analysis host (the system receiving packets via <code>server_bind</code> or legacy <code>mirror_bind</code>) must also have the <code>sipport</code> directive configured with the same list of ports used by all probes.
::<syntaxhighlight lang="ini">
# /etc/voipmonitor.conf on the CENTRAL HOST
sipport = 5060,5061,5080,6060
</syntaxhighlight>
 
::4. Restart both services:
::Apply the configuration changes:
::<syntaxhighlight lang="bash">
# On both probe and central host
systemctl restart voipmonitor
</syntaxhighlight>
 
:For more details on distributed architecture configuration and packet mirroring, see [[Sniffer_distributed_architecture|Distributed Architecture: Client-Server Mode]].
 
;4. Check for a restrictive <code>filter</code>:
:If you have a BPF <code>filter</code> configured, ensure it is not accidentally excluding the traffic you want to see. For debugging, try commenting out the <code>filter</code> line entirely and restarting the sensor.
 
== Step 5: Check GUI Capture Rules (Causing Call Stops) ==
If <code>tshark</code> sees SIP traffic and the sniffer configuration appears correct, but the probe stops processing calls or shows traffic only on the network interface, GUI capture rules may be the culprit.
 
Capture rules configured in the GUI can instruct the sniffer to ignore ("skip") all processing for matched calls. This includes calls matching specific IP addresses or telephone number prefixes.
 
;1. Review existing capture rules:
:Navigate to '''GUI -> Capture rules''' and examine all rules for any that might be blocking your traffic.
:Look specifically for rules with the '''Skip''' option set to '''ON''' (displayed as "Skip: ON"). The Skip option instructs the sniffer to completely ignore matching calls (no files, RTP analysis, or CDR creation).
 
;2. Test by temporarily removing all capture rules:
:To isolate the issue, first create a backup of your GUI configuration:
:* Navigate to '''Tools -> Backup & Restore -> Backup GUI -> Configuration tables'''
:* This saves your current settings including capture rules
:* Delete all capture rules from the GUI
:* Click the '''Apply''' button to save changes
:* Reload the sniffer by clicking the green '''"reload sniffer"''' button in the control panel
:* Test if calls are now being processed correctly
:* If resolved, restore the configuration from the backup and systematically investigate the rules to identify the problematic one
 
;3. Identify the problematic rule:
:* After restoring your configuration, remove rules one at a time and reload the sniffer after each removal
:* When calls start being processed again, you have identified the problematic rule
:* Review the rule's match criteria (IP addresses, prefixes, direction) against your actual traffic pattern
:* Adjust the rule's conditions or Skip setting as needed
 
;4. Verify rules are reloaded:
:After making changes to capture rules, remember that changes are '''not automatically applied''' to the running sniffer. You must click the '''"reload sniffer"''' button in the control panel, or the rules will continue using the previous configuration.
 
For more information on capture rules, see [[Capture_rules]].
 
== Troubleshooting: Service Fails to Start with "failed read rsa key" Error ==
 
If the VoIPmonitor sniffer service fails to start and logs the error message "failed read rsa key," this indicates that the manager key cannot be loaded from the database.
 
=== Cause ===
 
The manager_key is stored in the <code>system</code> database table (identified by <code>type='manager_key'</code>) and is required for proper manager/sensor operations in distributed deployments. This error most commonly occurs when the <code>mysqlloadconfig</code> option in <code>voipmonitor.conf</code> is set to <code>no</code>, which prevents VoIPmonitor from loading configuration (including the manager_key) from the database.
 
=== Troubleshooting Steps ===
 
;1. Check for the error in system logs:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
# Check current mount options
tail -f /var/log/syslog | grep voipmonitor
mount | grep voipmonitor


# For CentOS/RHEL/AlmaLinux
# Recommended mount options for /var/spool/voipmonitor
tail -f /var/log/messages | grep voipmonitor
# Add to /etc/fstab: noatime,data=writeback,barrier=0
 
# WARNING: barrier=0 requires battery-backed RAID
# For systemd systems
journalctl -u voipmonitor -f
</syntaxhighlight>
</syntaxhighlight>


;2. Verify mysqlloadconfig setting:
'''Verify improvement:'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check if mysqlloadconfig is set to no in voipmonitor.conf
# After changes, monitor iostat
grep mysqlloadconfig /etc/voipmonitor.conf
iostat -xz 2 10
# %util should drop below 70%, await should decrease
</syntaxhighlight>
</syntaxhighlight>


If the output shows <code>mysqlloadconfig = no</code>, this is the cause of the issue.
=== Solution: CPU Bottleneck ===
 
;3. Fix the mysqlloadconfig setting:
<syntaxhighlight lang="bash">
# Edit the configuration file
nano /etc/voipmonitor.conf
 
# Either remove the mysqlloadconfig line entirely (defaults to yes)
# Or uncomment/set to yes:
# mysqlloadconfig = yes
 
# Restart the sniffer service
systemctl restart voipmonitor
 
# Check if it started successfully
systemctl status voipmonitor
</syntaxhighlight>


;4. Verify manager_key exists in database:
==== Identify CPU Bottleneck Using Manager Commands ====
<syntaxhighlight lang="sql">
-- Query the manager_key from the system table
SELECT * FROM voipmonitor.`system` WHERE type='manager_key'\G
</syntaxhighlight>


If no manager_key exists, check your VoIPmonitor installation and consider running the installer or contacting support to regenerate the key.
VoIPmonitor provides manager commands to monitor thread CPU usage in real-time. This is essential for identifying which thread is saturated.


;5. Check database connectivity and permissions:
'''Connect to manager interface:'''
Verify that the VoIPmonitor sniffer can connect to the database and has read access to the <code>system</code> table.
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Test database connectivity with the configured credentials
# Via Unix socket (local, recommended)
mysql -h <mysqlhost> -u <mysqlusername> -p <mysqldb>
echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket
 
# Inside MySQL, verify the user has SELECT on voipmonitor.system
SHOW GRANTS FOR 'voipmonitor_user'@'%';
</syntaxhighlight>
 
;6. Check configuration consistency between probe and server:
In distributed deployments with probe and server components, ensure that both systems have consistent configuration in <code>/etc/voipmonitor.conf</code>. Specifically, both should have the same database connection settings and <code>mysqlloadconfig</code> should be enabled on both systems.
 
=== Summary ===
 
The "failed read rsa key" error is almost always caused by <code>mysqlloadconfig=no</code> in <code>voipmonitor.conf</code>. The solution is to remove or change this setting to <code>yes</code>, then restart the service.


== Step 6: Check VoIPmonitor Logs for Errors ==
# Via TCP port 5029 (remote or local)
Finally, VoIPmonitor's own logs are the best source for clues. Check the system log for any error messages generated by the sensor on startup or during operation.
echo 'sniffer_threads' | nc 127.0.0.1 5029
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
tail -f /var/log/syslog | grep voipmonitor


# For CentOS/RHEL/AlmaLinux
# Monitor continuously (every 2 seconds)
tail -f /var/log/messages | grep voipmonitor
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket"
</syntaxhighlight>
</syntaxhighlight>
Look for errors like:
* "pcap_open_live(eth0) error: eth0: No such device" (Wrong interface name)
* "Permission denied" (The sensor is not running with sufficient privileges)
* Errors related to database connectivity.
* Messages about dropping packets.
== Step 7: Check for OOM (Out of Memory) Issues ==
If VoIPmonitor suddenly stops processing CDRs and a service restart temporarily restores functionality, the system may be experiencing OOM (Out of Memory) killer events. The Linux OOM killer terminates processes when available RAM is exhausted, and MySQL (<code>mysqld</code>) is a common target due to its memory-intensive nature.
;1. Check for OOM killer events in kernel logs:
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
grep -i "out of memory\|killed process" /var/log/syslog | tail -20


# For CentOS/RHEL/AlmaLinux
{{Note|1=TCP port 5029 is encrypted by default. For unencrypted access, set <code>manager_enable_unencrypted = yes</code> in voipmonitor.conf (security risk on public networks).}}
grep -i "out of memory\|killed process" /var/log/messages | tail -20


# Also check dmesg:
'''Example output:'''
dmesg | grep -i "killed process" | tail -10
</syntaxhighlight>
Typical OOM killer messages look like:
<syntaxhighlight lang="text">
<syntaxhighlight lang="text">
Out of memory: Kill process 1234 (mysqld) score 123 or sacrifice child
t0 - binlog1 fifo pcap read          (  12345) : 78.5  FIFO  99    1234
Killed process 1234 (mysqld) total-vm: 12345678kB, anon-rss: 1234567kB
t2 - binlog1 pb write                ( 12346) :  12.3              456
rtp thread binlog1 binlog1 0        (  12347) :  8.1              234
rtp thread binlog1 binlog1 1        ( 12348) :  6.2              198
t1 - binlog1 call processing        (  12349) :   4.5              567
tar binlog1 compression 0            (  12350) :   3.2                89
</syntaxhighlight>
</syntaxhighlight>


;2. Monitor current memory usage:
'''Column interpretation:'''
<syntaxhighlight lang="bash">
{| class="wikitable"
# Check available memory (look for low 'available' or 'free' values)
|-
free -h
! Column !! Description
|-
| Thread name || Descriptive name (t0=capture, t1=call processing, t2=packet buffer write)
|-
| (TID) || Linux thread ID (useful for <code>top -H -p TID</code>)
|-
| CPU % || Current CPU usage percentage - '''key metric'''
|-
| Sched || Scheduler type (FIFO = real-time, empty = normal)
|-
| Priority || Thread priority
|-
| CS/s || Context switches per second
|}


# Check per-process memory usage (sorted by RSS)
'''Critical threads to watch:'''
ps aux --sort=-%mem | head -15
{| class="wikitable"
 
|-
# Check MySQL memory usage in bytes
! Thread !! Role !! If at 90-100%
cat /proc/$(pgrep mysqld)/status | grep -E "VmSize|VmRSS"
|-
</syntaxhighlight>
| '''t0''' (pcap read) || Packet capture from NIC || '''Single-core limit reached!''' Cannot parallelize. Need DPDK/Napatech.
Warning signs:
* '''Available memory consistently below 500MB during operation'''
* '''MySQL consuming most of the available RAM'''
* '''Swap usage near 100% (if swap is enabled)'''
* '''Frequent process restarts without clear error messages'''
 
;3. Solution: Increase physical memory:
The definitive solution for OOM-related CDR processing issues is to upgrade the server's physical RAM. After upgrading:
* Verify memory improvements with <code>free -h</code>
* Monitor for several days to ensure OOM events stop
* Consider tuning <code>innodb_buffer_pool_size</code> in your MySQL configuration to use the additional memory effectively
 
Additional mitigation strategies (while planning for RAM upgrade):
* Reduce MySQL's memory footprint by lowering <code>innodb_buffer_pool_size</code> (e.g., from 16GB to 8GB)
* Disable or limit non-essential VoIPmonitor features (e.g., packet capture storage, RTP analysis)
* Ensure swap space is properly configured as a safety buffer (though swap is much slower than RAM)
* Use <code>sysctl vm.swappiness=10</code> to favor RAM over swap when some memory is still available
 
=== Troubleshooting: Runaway Processes Causing OOM ===
 
If the sniffer is being killed by the OOM killer but increasing RAM or tuning MySQL configuration does not resolve the issue, the root cause may be '''external runaway processes''' spawned by scripts or other applications on the sensor host.
 
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
|-
! colspan="2" style="background:#ffc107;" | Differentiating OOM Scenarios
| '''t2''' (pb write) || Packet buffer processing || Processing bottleneck. Check t2CPU breakdown.
|-
|-
| style="vertical-align: top;" | '''MySQL killed by OOM'''
| '''rtp thread''' || RTP packet processing || Threads auto-scale. If still saturated, consider DPDK/Napatech.
| Database consuming RAM. Solution: Tune innodb_buffer_pool_size, add RAM, enable query_cache=yes in voipmonitor.conf.
|-
|-
| style="vertical-align: top;" | '''voipmonitor killed by OOM'''
| '''tar compression''' || PCAP archiving || I/O bottleneck (compression waiting for disk)
| Sniffer internal buffers. Solution: Reduce max_buffer_mem, lower ringbuffer, check query_cache setting.
|-
|-
| style="vertical-align: top;" | '''Runaway external processes causing OOM'''
| '''mysql store''' || Database writes || Database bottleneck. Check SQLq metric.
| Other processes spawned by scripts/consum RAM. Solution: Identify and disable problematic script, kill orphaned processes (this section).
|}
|}


== Diagnosis: Identify Runaway Processes ==
{{Warning|If '''t0 thread is at 90-100%''', you have hit the fundamental single-core capture limit. The t0 thread reads packets from the kernel and '''cannot be parallelized'''. Disabling features like jitterbuffer will NOT help - those run on different threads. The only solutions are:
* '''Reduce captured traffic''' using <code>interface_ip_filter</code> or BPF <code>filter</code>
* '''Use kernel bypass''' ([[DPDK]] or [[Napatech]]) which eliminates kernel overhead entirely}}


;Step 1: Check which process was killed by OOM:
==== Interpreting t2CPU Detailed Breakdown ====
Examine OOM killer messages to identify which process was sacrificed:
<syntaxhighlight lang="bash">
# Check for OOM events and identify killed processes
grep -i "out of memory\|killed process" /var/log/syslog | tail -10


# Alternative on some systems
The syslog status line shows <code>t2CPU</code> with detailed sub-metrics:
dmesg | grep -i "killed process"
<syntaxhighlight lang="text">
t2CPU[pb:10/ d:39/ s:24/ e:17/ c:6/ g:6/ r:7/ rm:24/ rh:16/ rd:19/]
</syntaxhighlight>
</syntaxhighlight>


If <code>voipmonitor</code> or another critical service is being killed, but MySQL/voipmonitor configuration is already optimized and RAM limits are reasonable, suspect runaway external processes.
{| class="wikitable"
 
|-
;Step 2: Identify resource-intensive processes:
! Code !! Function !! High Value Indicates
Look for processes with unusually high counts or memory consumption:
|-
<syntaxhighlight lang="bash">
| '''pb''' || Packet buffer output || Buffer management overhead
# Check all processes sorted by memory usage (high RSS)
|-
ps aux --sort=-%mem | head -20
| '''d''' || Dispatch || Structure creation bottleneck
 
|-
# Count processes by name (look for suspiciously high counts)
| '''s''' || SIP parsing || Complex/large SIP messages
ps aux | awk '{print $11}' | sort | uniq -c | sort -rn | head -15
|-
 
| '''e''' || Entity lookup || Call table lookup overhead
# Check for specific process types (replace with process name)
|-
ps ax | grep <process_name> | wc -l
| '''c''' || Call processing || Call state machine processing
</syntaxhighlight>
|-
 
| '''g''' || Register processing || High REGISTER volume
Warning signs for runaway processes:
|-
* Hundreds or thousands of instances of the same process
| '''r, rm, rh, rd''' || RTP processing stages || High RTP volume (threads auto-scale)
* Processes consuming excessive memory (RSS column)
|}
* Processes created in rapid succession
* Parent-child process chains that do not terminate
 
;Step 3: Find the parent spawning script:
Once you identify the runaway process, find its parent and the script responsible:
<syntaxhighlight lang="bash">
# Find the parent process of the runaway process
ps -ef | grep <runaway_process_name>
 
# Process tree to see the parent-child relationship
pstree -p | grep <runaway_process_name>
 
# Locate the parent script (check path from output above)
ls -la <path_to_parent_script>
</syntaxhighlight>
 
Common locations for problematic scripts:
* Cron jobs (<code>/etc/cron.*</code> directories, user crontabs)
* Systemd services (<code>/etc/systemd/system/</code>)
* Custom monitoring or management scripts
* Initialization scripts in <code>/etc/init.d/</code>
 
=== Step 4: Disable the Problematic Script ===
 
After identifying the parent script causing the runaway processes:
 
;Option A: Comment out or remove the script entry:
<syntaxhighlight lang="bash">
# If it's a cron job, edit the crontab
crontab -e
# Comment out the problematic line with #
 
# If it's a system cron script
chmod -x /etc/cron.daily/<script_name>
 
# If it's in a cron directory
rm /etc/cron.d/<script_name>
</syntaxhighlight>
 
;Option B: Add exit at the beginning of the script:
If you cannot remove the script entirely, disable it by preventing it from running:
<syntaxhighlight lang="bash">
# Edit the script
nano /path/to/problematic_script.sh
 
# Add 'exit' as the first line
exit
# (rest of script content below)
</syntaxhighlight>
 
The <code>exit</code> command at the top ensures the script terminates immediately without spawning any processes.
 
;Option C: For systemd services, disable the service:
<syntaxhighlight lang="bash">
# Stop and disable the problematic service
systemctl stop <service_name>
systemctl disable <service_name>
 
# Verify it will not start on boot
systemctl is-enabled <service_name>  # Should return "disabled"
</syntaxhighlight>
 
=== Step 5: Kill All Orphaned Processes ===
 
After disabling the parent script, terminate all existing runaway processes:
<syntaxhighlight lang="bash">
# Kill all instances of a specific process
killall <process_name>
 
# If kill does not work, force kill
killall -9 <process_name>
 
# Verify no processes remain
ps ax | grep <process_name>
</syntaxhighlight>
 
{{Warning|Using <code>killall -9</code> will force-terminate processes. Use only for runaway processes that you have positively identified as problematic.}}
 
=== Step 6: Verify Stability ===
 
After disabling the script and cleaning up processes:
 
;1. Monitor memory usage:
<syntaxhighlight lang="bash">
# Check current free memory
free -h
 
# Watch memory usage in real-time
watch -n 2 free -h
</syntaxhighlight>
 
;2. Monitor for new OOM events:
<syntaxhighlight lang="bash">
# Watch syslog for new OOM killer events
tail -f /var/log/syslog | grep -i "out of memory"
</syntaxhighlight>
 
;3. Verify voipmonitor service stability:
<syntaxhighlight lang="bash">
# Check service status
systemctl status voipmonitor
 
# Monitor service logs
tail -f /var/log/syslog | grep voipmonitor
</syntaxhighlight>
 
;4. Monitor process counts:
<syntaxhighlight lang="bash">
# Check that runaway processes are not respawning
watch -n 5 'ps ax | grep <process_name> | wc -l'
</syntaxhighlight>
 
If the process count remains at 0 or a low, stable number and no new OOM events occur over several hours, the issue is resolved.
 
=== Prevention and Best Practices ===
 
To prevent future runaway process issues:
 
'''Review cron jobs regularly:'''
* Audit all cron entries on the sensor host: <code>crontab -l</code>, <code>/etc/cron.*</code>
* Remove unnecessary or outdated scripts
* Check run frequency to avoid overlapping script executions
 
'''Monitor process counts:'''
* Implement monitoring to alert when process counts for specific services exceed thresholds
* Use tools like Nagios, Zabbix, or VoIPmonitor's own alerting to track system load
 
'''Use resource limits:'''
* Consider using <code>ulimit</code> or systemd's <code>MemoryMax</code> to cap memory usage for non-critical services
* Docker or other containerization solutions can provide process isolation and resource limits
 
== Step 8: PACKETBUFFER Saturation Under High Load ==
If a newly deployed sensor is experiencing memory filling up, crashes, and truncated RTP streams even with minimal traffic, the root cause is likely PACKETBUFFER saturation. This occurs when the sensor's internal packet buffer cannot keep up with the incoming packet rate, causing dropped packets and incomplete RTP stream recording.
 
=== Symptoms ===
* VoIPmonitor process or sensor crashes under load
* Syslog shows "PACKETBUFFER: memory is FULL" errors
* RTP streams are truncated or incomplete in PCAP files
* Memory usage increases steadily during high traffic periods
* Truncated PCAP files indicate forced disk writes or process termination
{{Note|This is different from OOM (Out of Memory) issues where the OOM killer terminates processes. PACKETBUFFER saturation is an internal VoIPmonitor buffer that fills when packet processing cannot keep up with the packet rate.}}
 
=== Diagnosis: Check for PACKETBUFFER Errors ===
;1. Monitor syslog for PACKETBUFFER saturation messages:
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
tail -f /var/log/syslog | grep -i packetbuffer
 
# For CentOS/RHEL
tail -f /var/log/messages | grep -i packetbuffer
</syntaxhighlight>
 
Look for error messages such as:
<code>PACKETBUFFER: memory is FULL</code>
<code>dropping packet because packetbuffer is full</code>
 
;2. Check sensor statistics in the GUI:
:* Navigate to '''Settings > Sensors'''
:* Expand the status for the affected sensor
:* Look for "# packet drops" counter or PACKETBUFFER-related errors


;3. Check CPU thread distribution:
'''Thread auto-scaling:''' VoIPmonitor automatically spawns additional threads when load increases:
<syntaxhighlight lang="bash">
* If '''d''' > 50% → SIP parsing thread ('''s''') starts
# View real-time CPU usage per thread
* If '''s''' > 50% → Entity lookup thread ('''e''') starts
top -H -p $(pgrep voipmonitor)
* If '''e''' > 50% → Call/register/RTP threads start
</syntaxhighlight>
If one thread is at 100% CPU while others are idle, this indicates a threading bottleneck causing PACKETBUFFER saturation.


=== Solution: Increase Threading and Buffer Memory ===
==== Configuration for High Traffic (>10,000 calls/sec) ====
;1. Increase RTP processing threads:
Edit <code>/etc/voipmonitor.conf</code> and add or modify:
<syntaxhighlight lang="ini">
# Increase starting number of RTP threads (default is CPU count or rtpthreads value)
# For high concurrent call loads (8,000-10,000+ calls), set to approximately half of CPU count
rtpthreads_start = 8


# Alternatively, set specific thread count higher if needed
rtpthreads_start = 16
</syntaxhighlight>
;2. Increase packet buffer memory:
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Increase maximum buffer memory from default 2000 MB to prevent PACKETBUFFER saturation
# /etc/voipmonitor.conf
# Ensure sufficient system RAM is available (this memory is used for packet buffering)
max_buffer_mem = 13000
</syntaxhighlight>
{{Warning|Setting <code>max_buffer_mem</code> too high on systems with limited RAM can cause OOM issues. Monitor memory usage after increasing this value.}}


;3. Enable or verify threading_expanded mode:
# Increase buffer to handle processing spikes (value in MB)
<syntaxhighlight lang="ini">
# 10000 = 10 GB - can go higher (20000, 30000+) if RAM allows
# Ensure threading_expanded is enabled (should be yes by default)
# Larger buffer absorbs I/O and CPU spikes without packet loss
# This enables the modern multi-threaded processing engine that auto-scales threads
max_buffer_mem = 10000
threading_expanded = yes
</syntaxhighlight>
{{Warning|Do not enable <code>threading_mod = 4</code> as this is deprecated. Only consider the legacy <code>threading_mod = 1</code> for single-threaded processing in extremely limited CPU scenarios as a last resort.}}


;4. For very high traffic environments (multi-gigabit or 8000+ concurrent calls):
# Use IP filter instead of BPF (more efficient)
<syntaxhighlight lang="ini">
interface_ip_filter = 10.0.0.0/8
# Enable high-traffic optimization
interface_ip_filter = 192.168.0.0/16
t2_boost = high_traffic
# Comment out any 'filter' parameter
 
# Set threading_expanded to high_traffic mode for environments exceeding 5 Gbit/s
threading_expanded = high_traffic
</syntaxhighlight>
</syntaxhighlight>


=== Verification After Configuration Changes ===
==== CPU Optimizations ====
;1. Restart the VoIPmonitor service:
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
</syntaxhighlight>
 
;2. Monitor syslog during a high-traffic window:
<syntaxhighlight lang="bash">
tail -f /var/log/syslog | grep -i packetbuffer
</syntaxhighlight>
The PACKETBUFFER saturation errors should no longer appear.
 
;3. Verify RTP streams are complete:
Make several test calls and verify:
* Download the PCAP file for each call in the GUI
* Open the PCAP in Wireshark or tshark
* Check that RTP streams are complete and not truncated
<syntaxhighlight lang="bash">
# Count RTP packets in a captured PCAP
tshark -r /path/to/capture.pcap -Y "rtp" | wc -l
</syntaxhighlight>
 
;4. Monitor memory stability:
<syntaxhighlight lang="bash">
# Watch memory usage
watch -n 5 free -h


# Check if OOM killer events have stopped
dmesg | grep -i "killed process" | tail -10
</syntaxhighlight>
Memory usage should stabilize and not grow indefinitely after applying these changes.
=== Additional Configuration for Distributed Client/Server Mode ===
If using <code>packetbuffer_sender = yes</code> to forward packets from remote probes to a central server, additional tuning is required:
;1. Enable packet buffer compression on the probe:
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Enable compression to reduce network transfer rate to central server
# /etc/voipmonitor.conf
# This prevents PACKETBUFFER saturation when network bandwidth is a bottleneck
packetbuffer_compress = yes
</syntaxhighlight>
 
;2. Increase max_buffer_mem on the central server:
The central server processing the mirrored traffic needs higher buffer memory:
<syntaxhighlight lang="ini">
# On the central server receiving packets
max_buffer_mem = 10000
</syntaxhighlight>
 
{{Note|When using <code>packetbuffer_sender = yes</code>, these settings must be applied on the '''receiving central server''', not the probe itself. The probe forwards all packets including RTP to the central server for processing.}}
 
=== Related Documentation ===
For complete details on these parameters, see [[Sniffer_configuration#Core_Threading_Model|Core Threading Model]] and [[Scaling|Scaling and Performance Tuning]].
 
== Step 9: Troubleshooting System Instability Due to Storage Hardware Failure ==
 
If your VoIPmonitor sensor is showing as disconnected (red X in GUI) and the overall system is unstable (frequent crashes, sluggish performance, or unexpected restarts), the root cause may be **storage hardware failure**.
 
When the disk subsystem fails, VoIPmonitor cannot write packets or persist data, leading to critical log messages like:
* <code>packetbuffer: MEMORY IS FULL</code>
* <code>DROPPED PACKETS</code>
 
{{Warning|1=Do NOT confuse storage hardware failure with PACKETBUFFER saturation (Step 8). PACKETBUFFER saturation is due to high traffic load and is resolved by increasing threads and buffer memory. Storage hardware failure is due to physical disk problems and requires hardware replacement.}}
 
=== Symptoms of Storage Hardware Failure ===
 
* Sensors showing as disconnected (red X) in the GUI
* System becoming unstable during normal operation
* Log messages indicating packetbuffer memory is full or packets being dropped
* Slow I/O operations, increased latency for database queries
* Intermittent service restarts or crashes
* Filesystem corruption errors in system logs
* Symptoms occur even with low or moderate traffic (unlike PACKETBUFFER saturation)
 
=== Step 1: Check VoIPmonitor Service Logs for Storage Issues ===
 
Examine the VoIPmonitor logs for evidence of storage problems:


<syntaxhighlight lang="bash">
# Reduce jitterbuffer calculations to save CPU (keeps MOS-F2 metric)
# Check voipmonitor service logs for packetbuffer or DROPPED messages
jitterbuffer_f1 = no
grep -E "packetbuffer.*MEMORY IS FULL|DROPPED PACKET" /var/log/syslog | tail -50
jitterbuffer_f2 = yes
jitterbuffer_adapt = no


# For systemd systems
# If MOS metrics are not needed at all, disable everything:
journalctl -u voipmonitor | grep -E "packetbuffer|DROPPED" | tail -50
# jitterbuffer_f1 = no
# jitterbuffer_f2 = no
# jitterbuffer_adapt = no
</syntaxhighlight>
</syntaxhighlight>


=== Step 2: Use smartctl to Check Disk Health ===
==== Kernel Bypass Solutions (Extreme Loads) ====
 
The <code>smartctl</code> utility allows you to check the health status and error counters of physical disks in the storage array.
 
<syntaxhighlight lang="bash">
# Identify all block devices (disks)
lsblk
 
# Check SMART health status for each disk
smartctl -H /dev/sda
smartctl -H /dev/sdb


# Get detailed information including error counters
When t0 thread hits 100% on standard NIC, kernel bypass is the only solution:
smartctl -a /dev/sda | grep -E "SMART overall-health|Errors|Reallocated|Pending|Runtime"
</syntaxhighlight>


{| class="wikitable"
{| class="wikitable"
|-
|-
! SMART Metric !! What It Indicates !! Action Required
! Solution !! Type !! CPU Reduction !! Use Case
|-
! ID 5: Reallocated Sector Count
| Bad sectors have been remapped. Non-zero value indicates disk degradation
| Monitor closely; replace if growing
|-
! ID 10: Spin Retry Count
| Drive had to retry spinning up platters. Indicates mechanical problems
| Replace disk immediately
|-
|-
! ID 197: Current Pending Sector Count
| '''[[DPDK]]''' || Open-source || ~70% || Multi-gigabit on commodity hardware
| Bad sectors waiting to be remapped. Data may be corrupted
| Backup immediately; replace disk
|-
|-
! ID 198: Uncorrectable Sector Count
| '''[[Napatech]]''' || Hardware SmartNIC || >97% (< 3% at 10Gbit) || Extreme performance requirements
| Drive encountered read/write errors it could not correct
| Replace disk immediately
|-
! SMART overall-health
| "FAILED" means disk is critically damaged and should be replaced
| Replace immediately
|}
|}


=== Step 3: Check System Logs for Filesystem Corruption ===
==== Verify Improvement ====


Kernel logs often reveal filesystem or journal corruption errors indicating storage problems.
<syntaxhighlight lang="bash">
# Monitor thread CPU after changes
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket | head -10"


<syntaxhighlight lang="bash">
# Or monitor syslog
# Check dmesg for filesystem errors, I/O errors, or corruption
journalctl -u voipmonitor -f
dmesg | grep -E "I/O error|filesystem.*corrupt|journal.*error|EXT4-fs error" | tail -50
# t0CPU should drop, heap values should stay < 20%
</syntaxhighlight>
</syntaxhighlight>


Error patterns indicating storage failure: <code>Buffer I/O error on device sdX</code>, <code>EXT4-fs error</code>, <code>journal commit I/O error</code>, <code>RAID array mdX is degraded</code>, <code>Hardware Error</code>.
{{Note|1=After changes, monitor syslog <code>heap[A&#124;B&#124;C]</code> values - should stay below 20% during peak traffic. See [[Syslog_Status_Line]] for detailed metric explanations.}}


=== Step 4: Check RAID Array Status (if applicable) ===
== Storage Hardware Failure ==


'''Symptom''': Sensor shows disconnected (red X) with "DROPPED PACKETS" at low traffic volumes.
'''Diagnosis''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check mdadm software RAID status
# Check disk health
smartctl -a /dev/sda
 
# Check RAID status (if applicable)
cat /proc/mdstat
cat /proc/mdstat
mdadm --detail /dev/md0
mdadm --detail /dev/md0
</syntaxhighlight>
</syntaxhighlight>


If RAID state is "Degraded", replace the failed disk and rebuild the array. If "Failed", multiple disks have failed - risk of total data loss.
Look for reallocated sectors, pending sectors, or RAID degraded state. Replace failing disk.
 
=== Step 5: Replace Failing Hardware ===
 
1. Identify failing disk with <code>lsblk -o NAME,SIZE,TYPE,MOUNTPOINT,SERIAL</code>
2. Physically replace the failing drive with a new one
3. Rebuild array with <code>mdadm --add /dev/md0 /dev/sdX</code> and monitor with <code>cat /proc/mdstat</code>
4. Verify replacement with <code>smartctl -H /dev/sdX</code>
5. Restart VoIPmonitor: <code>systemctl restart voipmonitor</code>


=== Prevention: Monitor Storage Health Proactively ===
== OOM (Out of Memory) ==


* Enable SMART monitoring: Install smartmontools, enable smartd service, configure <code>/etc/smartd.conf</code> with <code>DEVICESCAN -H -m email@example.com</code>
=== Identify OOM Victim ===
* Set up RAID monitoring with cron script: <code>grep degraded /proc/mdstat</code>


=== Related Documentation ===
* [[Emergency_procedures|Diagnosing Database Bottlenecks]] - General database tuning
* [[IO_Measurement|IO Measurement]] - Benchmarking storage performance
== Step 10: Missing CDRs for Calls with Large Packets ==
If VoIPmonitor is capturing some calls successfully but missing CDRs for specific calls (especially those that seem to have larger SIP packets like INVITEs with extensive SDP), there are two common causes to investigate.
=== Cause 1: snaplen Packet Truncation (VoIPmonitor Configuration) ===
The <code>snaplen</code> parameter in <code>voipmonitor.conf</code> limits how many bytes of each packet are captured. If a SIP packet exceeds <code>snaplen</code>, it is truncated and the sniffer may fail to parse the call correctly.
;1. Check your current snaplen setting:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
grep snaplen /etc/voipmonitor.conf
# Check for OOM kills
dmesg | grep -i "out of memory\|oom\|killed process"
journalctl --since "1 hour ago" | grep -i oom
</syntaxhighlight>
</syntaxhighlight>
Default is 3200 bytes (6000 if SSL/HTTP is enabled).


;2. Test if packet truncation is the issue:
=== MySQL Killed by OOM ===
Use <code>tcpdump</code> with <code>-s0</code> (snap infinite) to capture full packets:
<syntaxhighlight lang="bash">
# Capture SIP traffic with full packet length
tcpdump -i eth0 -s0 -nn port 5060 -w /tmp/test_capture.pcap


# Analyze packet sizes with Wireshark or tshark
Reduce InnoDB buffer pool:
tshark -r /tmp/test_capture.pcap -T fields -e frame.len -Y "sip" | sort -n | tail -10
</syntaxhighlight>
If you see SIP packets larger than your <code>snaplen</code> value (e.g., 4000+ bytes), increase <code>snaplen</code> in <code>voipmonitor.conf</code>:
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
snaplen = 65535
# /etc/mysql/my.cnf
innodb_buffer_pool_size = 2G  # Reduce from default
</syntaxhighlight>
</syntaxhighlight>
Then restart the sniffer: <code>systemctl restart voipmonitor</code>.


=== Cause 2: MTU Mismatch (Network Infrastructure) ===
=== Voipmonitor Killed by OOM ===
If packets are being lost or fragmented due to MTU mismatches in the network path, VoIPmonitor may never receive the complete packets, regardless of <code>snaplen</code> settings.


;1. Diagnose MTU-related packet loss:
Reduce buffer sizes in voipmonitor.conf:
Capture traffic with tcpdump and analyze in Wireshark:
<syntaxhighlight lang="ini">
<syntaxhighlight lang="bash">
max_buffer_mem = 2000  # Reduce from default
# Capture traffic on the VoIPmonitor host
ringbuffer = 50        # Reduce from default
tcpdump -i eth0 -s0 host <pbx_ip_address> -w /tmp/mtu_test.pcap
</syntaxhighlight>
</syntaxhighlight>
Open the pcap in Wireshark and look for:
* Reassembled PDUs marked as incomplete
* TCP retransmissions for the same packet
* ICMP "Fragmentation needed" messages (Type 3, Code 4)
;2. Verify packet completeness:
In Wireshark, examine large SIP INVITE packets. If the SIP headers or SDP appear cut off or incomplete, packets are likely being lost in transit due to MTU issues.
;3. Identify the MTU bottleneck:
The issue is typically a network device with a lower MTU than the end devices. Common locations:
* VPN concentrators
* Firewalls
* Routers with tunnel interfaces
* Cloud provider gateways (typically 1500 bytes vs. standard 9000 jumbo frames)
To locate the problematic device, trace the MTU along the network path from the PBX to the VoIPmonitor sensor.
;4. Resolution options:
* Increase MTU on the bottleneck device to match the rest of the network (e.g., from 1500 to 9000 for jumbo frame environments)
* Enable Path MTU Discovery (PMTUD) on intermediate devices
* Ensure your switching infrastructure supports jumbo frames end-to-end if you are using them


For more information on the <code>snaplen</code> parameter, see [[Sniffer_configuration#Network_Interface_.26_Sniffing|Sniffer Configuration]].
=== Runaway External Process ===


=== Cause 3: External Source Packet Truncation (Traffic Mirroring/LBS Modules) ===
If packets are truncated or corrupted BEFORE they reach VoIPmonitor, changing <code>snaplen</code> will NOT fix the issue. This scenario occurs when using external SIP sources that have their own packet size limitations.
; Symptoms to identify this scenario:
* Large SIP packets (e.g., WebRTC INVITE with big Authorization headers ~4k) appear truncated
* Packets show as corrupted or malformatted in VoIPmonitor GUI
* Changing <code>snaplen</code> in <code>voipmonitor.conf</code> has no effect
* Using TCP instead of UDP in the external system does not resolve the issue
; Common external sources that may truncate packets:
# Kamailio <code>siptrace</code> module
# FreeSWITCH <code>sip_trace</code> module
# OpenSIPS tracing modules
# Custom HEP/HOMER agent implementations
# Load balancers or proxy servers with traffic mirroring
; Diagnose external source truncation:
Use <code>tcpdump</code> with <code>-s0</code> (snap infinite) on the VoIPmonitor sensor to compare packet sizes:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Capture traffic received by VoIPmonitor
# Find memory-hungry processes
sudo tcpdump -i eth0 -s0 -nn port 5060 -w /tmp/voipmonitor_input.pcap
ps aux --sort=-%mem | head -20


# Analyze actual packet sizes received
# Kill orphaned/runaway process
tshark -r /tmp/voipmonitor_input.pcap -T fields -e frame.len -Y "sip.Method == INVITE" | sort -n | tail -10
kill -9 <PID>
</syntaxhighlight>
</syntaxhighlight>
For servers limited to '''16GB RAM''' or when experiencing repeated MySQL OOM kills:


If:
<syntaxhighlight lang="ini">
* You see packets with truncated SIP headers or incomplete SDP
# /etc/my.cnf or /etc/mysql/mariadb.conf.d/50-server.cnf
* The packet length is much smaller than expected (e.g., 1500 bytes instead of 4000+ bytes)
[mysqld]
* Truncation is consistent across all calls
# On 16GB server: 6GB buffer pool + 6GB MySQL overhead = 12GB total
# Leaves 4GB for OS + GUI, preventing OOM
innodb_buffer_pool_size = 6G


Then the external source is truncating packets before they reach VoIPmonitor.
# Enable write buffering (may lose up to 1s of data on crash but reduces memory pressure)
 
innodb_flush_log_at_trx_commit = 2
; Solutions for Kamailio siptrace truncation:
If using Kamailio's <code>siptrace</code> module with traffic mirroring:
 
1. Configure Kamailio to use TCP transport for siptrace (may help in some cases):
<syntaxhighlight lang="ini">
# In kamailio.cfg
modparam("siptrace", "duplicate_uri", "sip:voipmonitor_ip:port;transport=tcp")
</syntaxhighlight>
</syntaxhighlight>


2. If Kamailio reports "Connection refused", VoIPmonitor does not open a TCP listener by default. Manually open one:
Restart MySQL after changes:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Open TCP listener using socat
systemctl restart mysql
socat TCP-LISTEN:5888,fork,reuseaddr &
# or
</syntaxhighlight>
systemctl restart mariadb
Then update kamailio.cfg to use the specified port instead of the standard SIP port.
 
3. Use HAProxy traffic 'tee' function (recommended):
If your architecture includes HAProxy in front of Kamailio, use its traffic mirroring to send a copy of the WebSocket traffic directly to VoIPmonitor's standard SIP listening port. This bypasses the siptrace module entirely and preserves original packets:
<syntaxhighlight lang="text">
# In haproxy.cfg, within your frontend/backend configuration
# Send a copy of traffic to VoIPmonitor
option splice-response
tcp-request inspect-delay 5s
tcp-request content accept if { req_ssl_hello_type 1 }
use-server voipmonitor if { req_ssl_hello_type 1 }
listen voipmonitor_mirror
    bind :5888
    mode tcp
    server voipmonitor <voipmonitor_sensor_ip>:5060 send-proxy
</syntaxhighlight>
</syntaxhighlight>
=== SQL Queue Growth from Non-Call Data ===


Note: The exact HAProxy configuration depends on your architecture and whether you are mirroring TCP (WebSocket) or UDP traffic.
If <code>sip-register</code>, <code>sip-options</code>, or <code>sip-subscribe</code> are enabled, non-call SIP-messages (OPTIONS, REGISTER, SUBSCRIBE, NOTIFY) can accumulate in the database and cause the SQL queue to grow unbounded. This increases MySQL memory usage and leads to OOM kills of mysqld.
 
; Solutions for other external sources:
# Check the external system's documentation for packet size limits or truncation settings
# Consider using standard network mirroring (SPAN/ERSPAN/GRE) instead of SIP tracing modules
# Ensure the external system captures full packet lengths (disable any internal packet size caps)
# Verify that the external system does not reassemble or modify SIP packets before forwarding
 
== Troubleshooting: CDR Shows 000 No Response Despite Valid SIP Response ==
 
If the CDR View displays "000 No Response" in the Last Response column for calls that actually have valid final SIP response codes (such as 403 Forbidden, 500 Server Error, etc.), this indicates that the sniffer is receiving response packets but failing to correlate them with their corresponding INVITE transactions before writing the CDR.
 
=== Diagnosis: Verify Response Packets Are Captured ===
 
;1. Locate the affected call in the CDR View:
:* Find a call showing "000 No Response" in the Last Response column.
 
;2. Check the SIP History:
:* Click the [+] icon to expand the call's detail view.
:* Open the "SIP History" tab.
:* Look for the actual SIP response (e.g., 403 Forbidden, 486 Busy Here, 500 Internal Server Error).
 
If the response packet IS present in SIP History, the issue is a correlation timing problem. Proceed to the solution below.
 
If the response packet is NOT present in SIP History, the issue is a network visibility problem (see [[#SPAN_Configuration_Troubleshooting|Step 3: Investigate Packet Encapsulation]] and other network troubleshooting sections).
 
=== Root Cause: libpcap Packet Queue Timeout ===
 
The issue is caused by VoIPmonitor's libpcap packet capture timing out before responses can be matched to their originating INVITEs. This typically occurs in high-traffic environments or when packet processing is temporarily delayed due to system load.
 
The sniffer creates CDR records based on SIP INVITE packets. It attempts to correlate subsequent SIP responses (403, 500, etc.) with the original INVITE. If the packet queue processing is too slow or the time window is too short, responses arrive after the CDR has already been written with "Last Response" set to 0.
 
=== Solution: Configure libpcap Nonblocking Mode ===


Edit the "/etc/voipmonitor.conf" file on the sniffer host and add the following parameters:
{{Warning|1=Even with reduced <code>innodb_buffer_pool_size</code>, SQL queue will grow indefinitely without cleanup of non-call data.}}


'''Solution: Enable automatic cleanup of old non-call data'''
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Enable libpcap nonblocking mode to prevent packet queue blocking
# /etc/voipmonitor.conf
libpcap_nonblock_mode = yes
# cleandatabase=2555 automatically deletes partitions older than 7 years
 
# Covers: CDR, register_state, register_failed, and sip_msg (OPTIONS/SUBSCRIBE/NOTIFY)
# Increase packet deque window length (in milliseconds) for response correlation
cleandatabase = 2555
# Default is often 2000ms, increasing to 5000ms gives more time for responses
pcap_queue_deque_window_length = 5000
</syntaxhighlight>
</syntaxhighlight>


Save the file and restart the voipmonitor service:
Restart the sniffer after changes:
 
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
systemctl restart voipmonitor
</syntaxhighlight>
</syntaxhighlight>


=== Additional Considerations ===
{{Note|See [[Data_Cleaning]] for detailed configuration options and other <code>cleandatabase_*</code> parameters.}}
== Service Startup Failures ==


;If the issue persists after applying the fix:
=== Interface No Longer Exists ===
:* Try increasing <code>pcap_queue_deque_window_length</code> further (e.g., to 7000 or 10000 milliseconds)
:* Check system load to ensure the server is not under heavy CPU or I/O pressure
:* Verify adequate <code>ringbuffer</code> size is configured for your traffic volume (see [[Scaling|Scaling and Performance Tuning]])


;For distributed architectures:
After OS upgrade, interface names may change (eth0 → ensXXX):
:* Ensure all voipmonitor hosts have synchronized time (see [[#Verify_System_Time_Synchronization]])
:* Time mismatches between components can cause correlation failures


{{Note|The <code>pcap_queue_deque_window_length</code> parameter is also used in distributed mirroring scenarios to sort packets from multiple mirrors. Increasing this value improves packet correlation in both single-sensor and distributed setups.}}
For more information on packet capture configuration, see [[Sniffer_configuration|Sniffer Configuration]].
== Step 9: Probe Timeout Due to Virtualization Timing Issues ==
If remote probes are intermittently disconnecting from the central server with timeout errors, even on a high-performance network with low load, the issue may be related to virtualization host timing problems rather than network connectivity.
=== Diagnosis: Check System Log Timing Intervals ===
The VoIPmonitor sensor generates status log messages approximately every 10 seconds during normal operation. If the timing system on the probe is inconsistent, the interval between these status messages can exceed 30 seconds, triggering a connection timeout.
;1. Monitor the system log on the affected probe:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
tail -f /var/log/syslog | grep voipmonitor
# Find current interface names
</syntaxhighlight>
ip a


;2. Examine the timestamps of voipmonitor status messages:
# Update all config locations
Look for repeating log entries that should appear approximately every 10 seconds during normal operations.
grep -r "interface" /etc/voipmonitor.conf /etc/voipmonitor.conf.d/


;3. Identify timing irregularities:
# Also check GUI: Settings → Sensors → Configuration
Calculate the time interval between successive status log entries. '''If the interval exceeds 30 seconds''', this indicates a timing system problem that will cause connection timeouts with the central server.
 
=== Root Cause: Virtualization Host RDTSC Issues ===
 
This problem is '''not''' network-related. It is a host-level timing issue that impacts the application's internal timers.
 
The issue typically occurs on virtualized probes where the host's CPU timekeeping is inconsistent. Specifically, problems with the RDTSC (Read Time-Stamp Counter) CPU instruction on the virtualization host can cause:
 
* Irregular system clock behavior on the guest VM
* Application timers that do not fire consistently
* Sporadic timeouts in client-server connections
 
=== Resolution ===
 
;1. Investigate the virtualization host configuration:
Check the host's hypervisor or virtualization platform documentation for known timekeeping issues related to RDTSC.
 
Common virtualization platforms with known timing considerations:
* KVM/QEMU: Check CPU passthrough and TSC mode settings
* VMware: Verify time synchronization between guest and host
* Hyper-V: Review Integration Services time sync configuration
* Xen: Check TSC emulation settings
 
;2. Apply host-level fixes:
These are host-level fixes, not changes to the guest VM configuration. Consult your virtualization platform's documentation for specific steps to address RDTSC timing issues.
 
Typical solutions include:
* Enabling appropriate TSC modes on the host
* Configuring CPU features passthrough correctly
* Adjusting hypervisor timekeeping parameters
 
;3. Verify the fix:
After applying the host-level configuration changes, monitor the probe's status logs again to confirm that the timing intervals are now consistently around 10 seconds (never exceeding 30 seconds).
 
<syntaxhighlight lang="bash">
# Monitor for regular status messages
tail -f /var/log/syslog | grep voipmonitor
</syntaxhighlight>
</syntaxhighlight>


Once the timing is corrected, probe connections to the central server should remain stable without intermittent timeouts.
=== Missing Dependencies ===
 
== Troubleshooting: Audio Missing on One Call Leg ==
 
If the sniffer captures full audio on one call leg (e.g., carrier/outside) but only partial or no audio on the other leg (e.g., PBX/inside), use this diagnostic workflow to identify the root cause BEFORE applying any configuration fixes.
 
The key question to answer is: '''Are the RTP packets for the silent leg present on the wire?'''
 
=== Step 1: Use tcpdump to Capture Traffic During a Test Call ===
 
Initiate a new test call that reproduces the issue. During the call, use tcpdump or tshark directly on the sensor's sniffing interface to capture all traffic:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Capture traffic to a file during the test call
# Install common missing package
# Replace eth0 with your sniffing interface
apt install libpcap0.8  # Debian/Ubuntu
tcpdump -i eth0 -s0 -w /tmp/direct_capture.pcap
yum install libpcap    # RHEL/CentOS
 
# OR: Display live traffic for specific IPs (useful for real-time diagnostics)
tcpdump -i eth0 -s0 -nn "host <pbx_ip> or host <carrier_ip>"
</syntaxhighlight>
</syntaxhighlight>


Let the call run for 10-30 seconds, then stop tcpdump with Ctrl+C.
== Network Interface Issues ==
 
=== Step 2: Retrieve VoIPmonitor GUI's PCAP for the Same Call ===
 
After the call completes:
1. Navigate to the '''CDR View''' in the VoIPmonitor GUI
2. Find the test call you just made
3. Download the PCAP file for that call (click the PCAP icon/button)
4. Save it as: <code>/tmp/gui_capture.pcap</code>
 
=== Step 3: Compare the Two Captures ===


Analyze both captures to determine if RTP packets for the silent leg are present on the wire:
=== Promiscuous Mode ===


Required for SPAN port monitoring:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Count RTP packets in the direct capture
# Enable
tshark -r /tmp/direct_capture.pcap -Y "rtp" | wc -l
ip link set eth0 promisc on
 
# Count RTP packets in the GUI capture
tshark -r /tmp/gui_capture.pcap -Y "rtp" | wc -l
 
# Check for RTP from specific source IPs in the direct capture
tshark -r /tmp/direct_capture.pcap -Y "rtp" -T fields -e rtp.ssrc -e ip.src -e ip.dst


# Check Call-ID in both captures to verify they're the same call
# Verify
tshark -r /tmp/direct_capture.pcap -Y "sip" -T fields -e sip.Call-ID | head -1
ip link show eth0 | grep PROMISC
tshark -r /tmp/gui_capture.pcap -Y "sip" -T fields -e sip.Call-ID | head -1
</syntaxhighlight>
</syntaxhighlight>


=== Step 4: Interpret the Results ===
{{Note|Promiscuous mode is NOT required for ERSPAN/GRE tunnels where traffic is addressed to the sensor.}}
 
{| class="wikitable" style="background:#e7f3ff; border:1px solid #3366cc;"
|-
! colspan="2" style="background:#3366cc; color: white;" | Diagnostic Decision Matrix
|-
! Observation
! Root Cause & Next Steps
|-
| '''RTP packets for silent leg are NOT present in direct capture'''
| '''Network/PBX Issue:''' The PBX or network is not sending the packets. This is not a VoIPmonitor problem. Troubleshoot the PBX (check NAT, RTP port configuration) or network (SPAN/mirror configuration, firewall rules).
|-
| '''RTP packets for silent leg ARE present in direct capture but missing in GUI capture'''
| '''Sniffer Configuration Issue:''' Packets are on the wire but VoIPmonitor is failing to capture or correlate them. Likely causes: NAT IP mismatch (natalias configuration incorrect), SIP signaling advertises different IP than RTP source, or restrictive filter rules. Proceed with configuration fixes.
|-
| '''RTP packets present in both captures but audio still silent'''
| '''Codec/Transcoding Issue:''' Packets are captured correctly but may not be decoded properly. Check codec compatibility, unsupported codecs, or transcoding issues on the PBX.
|}
 
=== Step 5: Apply the Correct Fix Based on Diagnosis ===
 
;If RTP is NOT on the wire (Network/PBX issue):
* Check PBX RTP port configuration and firewall rules
* Verify network SPAN/mirror is capturing bidirectional traffic (see [[#SPAN_Configuration_Troubleshooting|Section 3]])
* Check PBX NAT settings - RTP packets may be blocked or routed incorrectly
 
;If RTP is on the wire but not captured (Sniffer configuration issue):


==== Check rtp_check_both_sides_by_sdp Setting (Primary Cause) ====
=== Interface Drops ===


This is the '''most common cause''' of one-way RTP capture when packets are present on the wire. The <code>rtp_check_both_sides_by_sdp</code> parameter controls how strictly RTP streams are correlated with SDP (Session Description Protocol) signaling.
Check the current setting in <code>/etc/voipmonitor.conf</code>:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
grep "^rtp_check_both_sides_by_sdp" /etc/voipmonitor.conf
# Check for drops
</syntaxhighlight>
ip -s link show eth0 | grep -i drop
 
If the setting is <code>yes</code> or <code>strict</code> or <code>very_strict</code>, this requires '''BOTH sides of RTP to exactly match SDP (SIP signaling)''':
* <code>strict</code>: Only allows verified packets after first match (blocks unverified)
* <code>very_strict</code>: Blocks all unverified packets (most restrictive)
* <code>keep_rtp_packets</code>: Same as <code>yes</code> but stores unverified packets for debugging
 
Symptoms of restrictive <code>rtp_check_both_sides_by_sdp</code> settings:
* Only one call leg appears in CDR (caller OR called, not both)
* Received packets column shows 0 or very low on one leg
* tcpdump shows both RTP streams present, but GUI captures only one
* Affects many calls, not just specific ones
 
'''Solution:''' Change to <code>no</code> or comment out the line:


<syntaxhighlight lang="ini">
# If drops present, increase ring buffer
; /etc/voipmonitor.conf
ethtool -G eth0 rx 4096
rtp_check_both_sides_by_sdp = no
</syntaxhighlight>
</syntaxhighlight>


Restart the sniffer to apply:
=== Bonded/EtherChannel Interfaces ===


<syntaxhighlight lang="bash">
'''Symptom''': False packet loss when monitoring bond0 or br0.
systemctl restart voipmonitor
</syntaxhighlight>


If you previously set <code>rtp_check_both_sides_by_sdp = yes</code> to solve audio mixing issues in multi-call environments where multiple calls share the same IP:port, consider using alternative approaches like <code>sdp_multiplication</code> instead, as enabling strict checking breaks one-way RTP capture.
'''Solution''': Monitor physical interfaces, not logical:
 
==== Other Configuration Checks ====
 
If checking <code>rtp_check_both_sides_by_sdp</code> does not resolve the issue, proceed with these additional diagnostic steps:
 
* Configure '''natalias''' in <code>/etc/voipmonitor.conf</code> to map the IP advertised in SIP signaling to the actual RTP source IP (NAT scenarios only):
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
; /etc/voipmonitor.conf
# voipmonitor.conf - use physical interfaces
natalias = <Public_IP_Signaled> <Private_IP_Actual>
interface = eth0,eth1
</syntaxhighlight>
</syntaxhighlight>
: When using <code>natalias</code>, ensure <code>rtp_check_both_sides_by_sdp</code> is set to <code>no</code> (the default).
* Check for restrictive <code>filter</code> directives in <code>voipmonitor.conf</code>
* Verify <code>sipport</code> includes all necessary SIP ports
;If packets are captured but audio silent (Codec issue):
* Check CDR view for codec information on both legs
* Verify VoIPmonitor GUI has the necessary codec decoders installed
* Check for codec mismatches between call legs (transcoding may be missing)


=== Step 6: Verify the Fix After Configuration Changes ===
=== Network Offloading Issues ===


After making changes in <code>/etc/voipmonitor.conf</code>:
'''Symptom''': Kernel errors like <code>bad gso: type: 1, size: 1448</code>


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Restart the sniffer
# Disable offloading on capture interface
systemctl restart voipmonitor
ethtool -K eth0 gso off tso off gro off lro off
 
# Make another test call and repeat the diagnostic workflow
# Compare direct vs GUI capture again
</syntaxhighlight>
</syntaxhighlight>


Confirm that RTP packets for the problematic leg now appear in both the direct tcpdump capture AND the GUI's PCAP file.
== Packet Ordering Issues ==


'''Note:''' This diagnostic methodology helps you identify whether the issue is in the network infrastructure (PBX, SPAN, firewall) or in VoIPmonitor configuration (natalias, filters). Applying VoIPmonitor configuration fixes when the root cause is a network issue will not resolve the problem.
If SIP messages appear out of sequence:


== Troubleshooting: Server Coredumps and SQL Queue Overload ==
'''First''': Rule out Wireshark display artifact - disable "Analyze TCP sequence numbers" in Wireshark. See [[FAQ]].


If the VoIPmonitor server is experiencing regular coredumps, the cause may be an SQL queue bottleneck that exceeds system limits. The SQL queue grows when the database cannot keep up with the rate of data being inserted from VoIPmonitor.
'''If genuine reordering''': Usually caused by packet bursts in network infrastructure. Use tcpdump to verify packets arrive out of order at the interface. Work with network admin to implement QoS or traffic shaping. For persistent issues, consider dedicated capture card with hardware timestamping (see [[Napatech]]).
{{Note|For out-of-order packets in '''client/server mode''' (multiple sniffers), see [[Sniffer_distributed_architecture]] for <code>pcap_queue_dequeu_window_length</code> configuration.}}


=== Symptoms ===
=== Solutions for SPAN/Mirroring Reordering ===


* Server crashes or coredumps regularly, often during peak traffic hours
If packets arrive out of order at the SPAN/mirror port (e.g., 302 responses before INVITE causing "000 no response" errors):
* Syslog messages showing a growing <code>SQLq</code> counter (SQL queries waiting)
* Crashes occur when OPTIONS, SUBSCRIBE, and NOTIFY messages are being processed at high volume


=== Identify the Root Cause ===
1. '''Configure switch to preserve packet order''': Many switches allow configuring SPAN/mirror ports to maintain packet ordering. Consult your switch documentation for packet ordering guarantees in mirroring configuration.


;1. Check the SQL queue metric in syslog:
2. '''Replace SPAN with TAP or packet broker''': Unlike software-based SPAN mirroring, hardware TAPs and packet brokers guarantee packet order. Consider upgrading to a dedicated TAP or packet broker device for mission-critical monitoring.
<syntaxhighlight lang="bash">
== Database Issues ==
# Debian/Ubuntu
tail -f /var/log/syslog | grep "SQLq"
 
# CentOS/RHEL
tail -f /var/log/messages | grep "SQLq"
</syntaxhighlight>
 
Look for the <code>SQLq[XXX]</code> value where XXX is the number of queued SQL commands. If this number is consistently growing or reaching high values (thousands or more), the database is a bottleneck.
 
;2. Check if SIP message processing is enabled:
<syntaxhighlight lang="bash">
grep -E "sip-options=|sip-subscribe=|sip-notify=" /etc/voipmonitor.conf
</syntaxhighlight>
 
If these are set to <code>yes</code> and you have a high volume of these messages (OPTIONS pings sent frequently by SIP devices), this can overwhelm the database insert thread queue.


=== Solutions ===
=== SQL Queue Overload ===


There are three approaches to resolve SQL queue overload coredumps:
'''Symptom''': Growing <code>SQLq</code> metric, potential coredumps.
 
==== Solution 1: Increase MySQL Insert Threads ====
 
Increase the number of threads dedicated to inserting SIP messages into the database. This allows more parallel database operations.
 
Edit <code>/etc/voipmonitor.conf</code> and add or modify:
 
<syntaxhighlight lang="ini">
# Increase insert threads for SIP messages (default is 4, increase to 8 or higher for high traffic)
mysqlstore_max_threads_sip_msg = 8
</syntaxhighlight>
 
Restart VoIPmonitor for the change to take effect:
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
</syntaxhighlight>
 
{{Tip|For very high traffic environments, you may need to increase this value further (e.g., 12 or 16).}}
 
==== Solution 2: Disable High-Volume SIP Message Types ====
 
Reduce the load on the SQL queue by disabling processing of specific high-volume SIP message types that are not needed for your analysis.
 
Edit <code>/etc/voipmonitor.conf</code>:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Disable processing and database storage for specific message types
# voipmonitor.conf - increase threads
sip-options = no
mysqlstore_concat_limit_cdr = 1000
sip-subscribe = no
cdr_check_exists_callid = 0
sip-notify = no
</syntaxhighlight>
 
Restart VoIPmonitor:
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
</syntaxhighlight>
</syntaxhighlight>


{{Note|See [[SIP_OPTIONS/SUBSCRIBE/NOTIFY]] for detailed information on these options and when to use <code>nodb</code> mode instead of disabling entirely.}}
=== Error 1062 - Lookup Table Limit ===
 
==== Solution 3: Optimize MySQL Performance ====
 
Tune the MySQL/MariaDB server for better write performance to handle the high insert rate from VoIPmonitor.


Edit your MySQL configuration file (typically <code>/etc/mysql/my.cnf</code> or <code>/etc/mysql/mariadb.conf.d/50-server.cnf</code>):
'''Symptom''': <code>Duplicate entry '16777215' for key 'PRIMARY'</code>


'''Quick fix''':
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
[mysqld]
# voipmonitor.conf
# InnoDB buffer pool size - set to approximately 50-70% of available RAM on a dedicated database server
cdr_reason_string_enable = no
# On servers running VoIPmonitor and MySQL together, use approximately 30-50% of RAM
innodb_buffer_pool_size = 8G
 
# Reduce transaction durability for faster writes (may lose up to 1 second of data on crash)
innodb_flush_log_at_trx_commit = 2
</syntaxhighlight>
 
Restart MySQL and VoIPmonitor:
<syntaxhighlight lang="bash">
systemctl restart mysql
systemctl restart voipmonitor
</syntaxhighlight>
</syntaxhighlight>


{{Warning|Setting <code>innodb_flush_log_at_trx_commit</code> to <code>2</code> trades some data safety for performance. In the event of a power loss or crash, up to 1 second of the most recent transactions may be lost.}}
See [[Database_troubleshooting#Database_Error_1062_-_Lookup_Table_Auto-Increment_Limit|Database Troubleshooting]] for complete solution.
 
==== Solution 4: Immediate SQL Queue Clearing ====


If CDRs have stopped appearing in the GUI for several days and the SQL queue (SQLq) is backed up, you can immediately clear the backlog by deleting queue files and restarting services.
== Bad Packet Errors ==


=== Symptoms for SQL Queue Backup ===
'''Symptom''': <code>bad packet with ether_type 0xFFFF detected on interface</code>


* No new CDRs appearing in the GUI for an extended period (days)
'''Diagnosis''':
* Sensor status shows a non-zero <code>SQLq</code> (SQL queue) count in '''Settings > Sensors'''
* The delay in CDRs equals the age of the oldest query file in the queue
 
=== Diagnose SQL Queue Status ===
 
;1. Check sensor status in the GUI:
:* Navigate to '''Settings > Sensors'''
:* Expand the status for the affected sensor
:* Look for a non-zero <code>SQLq</code> value
 
;2. Alternatively check via command line:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check for SQL queue messages in syslog
# Run diagnostic (let run 30-60 seconds, then kill)
grep "SQLq" /var/log/syslog | tail -20
voipmonitor --check_bad_ether_type=eth0


# Check for qoq* queue files in voipmonitor directory
# Find and kill the diagnostic process
# The default directory is typically /voipmonitor or /var/lib/voipmonitor
ps ax | grep voipmonitor
ls -la /voipmonitor/qoq*
kill -9 <PID>
</syntaxhighlight>
</syntaxhighlight>


=== Clear SQL Queue and Restart Processing ===
Causes: corrupted packets, driver issues, VLAN tagging problems. Check <code>ethtool -S eth0</code> for interface errors.


If the SQL queue is backed up and you want to resume processing immediately:
== Useful Diagnostic Commands ==


;1. Restart the voipmonitor and rsyslog services to begin processing the queue naturally:
=== tshark Filters for SIP ===
<syntaxhighlight lang="bash">
# Restart both services
systemctl restart voipmonitor
systemctl restart rsyslog
</syntaxhighlight>
 
;2. Monitor the SQLq count until it reaches zero. The delay in CDRs equals the age of the oldest query file in the queue.


;3. If the queue is too large or you want to skip old data and resume immediately, clear the queue files:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Stop the voipmonitor service first to prevent new data writes
# All SIP INVITEs
systemctl stop voipmonitor
 
# Delete all qoq* queue files from the voipmonitor directory
# Replace /voipmonitor with your actual directory path
rm -f /voipmonitor/qoq*
 
# Restart the voipmonitor service
systemctl start voipmonitor
</syntaxhighlight>
 
;4. After clearing the queue, monitor the <code>SQLf</code> (failed queries) stat in the sensor status:
:* Navigate to '''Settings > Sensors'''
:* Expand the status for the affected sensor
:* Watch for the <code>SQLf</code> counter
:* Ensure it remains low (e.g., below 10) and does not grow, indicating new queries are processing successfully
 
{{Warning|Deleting queue files permanently discards all pending CDR data. Only do this if you are willing to lose the queued data or if the backlog is so old that the data is no longer useful.}}
 
{{Tip|The voipmonitor directory location varies by installation. Common locations include <code>/voipmonitor</code>, <code>/var/lib/voipmonitor</code>, or the directory specified by the <code>pcap_dir</code> configuration option in <code>voipmonitor.conf</code>.}}
 
=== Additional Troubleshooting ===
 
* If increasing threads and disabling SIP message types do not resolve the issue, check if the database server itself has performance bottlenecks (CPU, disk I/O, memory)
* For systems with extremely high call volumes, consider moving the database to a separate dedicated server
* Monitor the <code>SQLq</code> metric after making changes to verify the queue is not growing unchecked
 
== Appendix: tshark Display Filter Syntax for SIP ==
When using <code>tshark</code> to analyze SIP traffic, it is important to use the '''correct Wireshark display filter syntax'''. Below are common filter examples:
 
=== Basic SIP Filters ===
<syntaxhighlight lang="bash">
# Show all SIP INVITE messages
tshark -r capture.pcap -Y "sip.Method == INVITE"
tshark -r capture.pcap -Y "sip.Method == INVITE"


# Show all SIP messages (any method)
# Find specific phone number
tshark -r capture.pcap -Y "sip"
 
# Show SIP and RTP traffic
tshark -r capture.pcap -Y "sip || rtp"
</syntaxhighlight>
 
=== Search for Specific Phone Number or Text ===
<syntaxhighlight lang="bash">
# Find calls containing a specific phone number (e.g., 5551234567)
tshark -r capture.pcap -Y 'sip contains "5551234567"'
tshark -r capture.pcap -Y 'sip contains "5551234567"'


# Find INVITE messages for a specific number
# Get Call-IDs
tshark -r capture.pcap -Y 'sip.Method == INVITE && sip contains "5551234567"'
tshark -r capture.pcap -Y "sip.Method == INVITE" -T fields -e sip.Call-ID
</syntaxhighlight>
 
=== Extract Call-ID from Matching Calls ===
<syntaxhighlight lang="bash">
# Get Call-ID for calls matching a phone number
tshark -r capture.pcap -Y 'sip.Method == INVITE && sip contains "5551234567"' -T fields -e sip.Call-ID
 
# Get Call-ID along with From and To headers
tshark -r capture.pcap -Y 'sip.Method == INVITE' -T fields -e sip.Call-ID -e sip.from.user -e sip.to.user
</syntaxhighlight>
 
=== Filter by IP Address ===
<syntaxhighlight lang="bash">
# SIP traffic from a specific source IP
tshark -r capture.pcap -Y "sip && ip.src == 192.168.1.100"
 
# SIP traffic between two hosts
tshark -r capture.pcap -Y "sip && ip.addr == 192.168.1.100 && ip.addr == 10.0.0.50"
</syntaxhighlight>
 
=== Filter by SIP Response Code ===
<syntaxhighlight lang="bash">
# Show all 200 OK responses
tshark -r capture.pcap -Y "sip.Status-Code == 200"


# Show all 4xx and 5xx error responses
# SIP errors (4xx, 5xx)
tshark -r capture.pcap -Y "sip.Status-Code >= 400"
tshark -r capture.pcap -Y "sip.Status-Code >= 400"
# Show 486 Busy Here responses
tshark -r capture.pcap -Y "sip.Status-Code == 486"
</syntaxhighlight>
=== Important Syntax Notes ===
* '''Field names are case-sensitive:''' Use <code>sip.Method</code>, <code>sip.Call-ID</code>, <code>sip.Status-Code</code> (not <code>sip.method</code> or <code>sip.call-id</code>)
* '''String matching uses <code>contains</code>:''' Use <code>sip contains "text"</code> (not <code>sip.contains()</code>)
* '''Use double quotes for strings:''' <code>sip contains "number"</code> (not single quotes)
* '''Boolean operators:''' Use <code>&&</code> (and), <code>||</code> (or), <code>!</code> (not)
For a complete reference, see the [https://www.wireshark.org/docs/dfref/s/sip.html Wireshark SIP Display Filter Reference].
== Database Error 1062 - Lookup Table Limit ==
{{Main|Database_troubleshooting#Database_Error_1062_-_Lookup_Table_Auto-Increment_Limit}}
If sniffer logs show <code>1062 - Duplicate entry '16777215' for key 'PRIMARY'</code> and CDRs stop being stored, this is caused by lookup tables (cdr_sip_response, cdr_reason) hitting the MEDIUMINT auto-increment limit.
'''Quick fix:''' Set <code>cdr_reason_string_enable = no</code> in voipmonitor.conf and restart the service. For complete troubleshooting steps including TRUNCATE and queue cleanup, see [[Database_troubleshooting#Database_Error_1062_-_Lookup_Table_Auto-Increment_Limit|Database Troubleshooting]].
== Routing Loops ==
Routing loops occur when SIP INVITE requests continuously circulate between SIP servers without completing, causing excessive traffic and call failures. Common symptoms include:
* High volume of calls to a single destination number in a short time period
* Many INVITE requests with no SIP response (response code 0)
* Very long Post Dial Delay (PDD) values
* Rapid retransmission of INVITE to the same called number
{{Note|Routing loops can be caused by misconfigured dial plans, incorrect SIP URI formats, or circular forwarding rules.}}
==== Detection Methods ====
Use alerts to detect routing loops:
* '''SIP Response Alert (Response code 0)''': Configure an alert to detect unreplied INVITE requests. [[Alerts|Configure this in GUI > Alerts]] by setting Response code to 0. This catches calls in a loop that never receive any SIP response.
* '''PDD (Post Dial Delay) Alert''': Configure a PDD alert with a threshold (e.g., <code>PDD > 30</code> seconds) to detect calls taking excessively long to complete. Routing loops often have very high PDD values as INVITEs continue retransmitting. [[Alerts|See Alerts documentation for PDD configuration]].
* '''Fraud: Sequential Alert''': Monitor for excessive calls to any single destination number within a short time window. Configure [[Anti-fraud|Fraud: Sequential]] with an appropriate Interval and Limit (e.g., 50 calls in 1 hour to the same number). Leave the called number field empty to monitor all destinations.
==== Troubleshooting Steps ====
1. Identify the looping destination number from alert logs or CDR search
2. Check the SIP dialog to trace the call path (use PCAP analysis in GUI)
3. Verify dial plan configuration on all involved SIP servers
4. Look for forwarding rules or translation patterns that may create circular routing
5. Fix the misconfiguration and verify the loop no longer occurs
== Service Fails to Start: Network Interface No Longer Exists ==
The voipmonitor service fails to start, reporting an error for a network interface that no longer exists and has been removed from the main configuration file.
=== Symptoms ===
* Service fails to start with interface-related error
* Error message references an interface name that was removed or renamed
* The interface is not listed in <code>ip a</code> output
=== Root Cause ===
VoIPmonitor may have cached interface configurations in additional configuration files beyond the main <code>voipmonitor.conf</code>.
=== Solution ===
Check for interface references in all configuration locations:
<syntaxhighlight lang="bash">
# 1. Check main config
grep -i "interface" /etc/voipmonitor.conf
# 2. Check for additional config files
ls -la /etc/voipmonitor.conf.d/
grep -r "interface" /etc/voipmonitor.conf.d/
# 3. Check sensor configuration stored in database (via GUI)
# Navigate to: Settings > Sensors > [Your Sensor] > Configuration
# 4. Remove or update references to the old interface
# Edit the relevant config file and change to the correct interface name:
nano /etc/voipmonitor.conf
# Change: interface = eth0  (old)
# To:    interface = ens192  (new)
# 5. Restart service
systemctl restart voipmonitor
</syntaxhighlight>
=== Prevention ===
When changing network interface names (e.g., during OS upgrade from eth0 to ensXXX naming):
1. Update <code>/etc/voipmonitor.conf</code> before reboot
2. Check for any additional config files in <code>/etc/voipmonitor.conf.d/</code>
3. Update sensor configuration in GUI if applicable
== Kernel Errors: "bad gso" or Network Offloading Issues ==
If you encounter kernel errors like <code>bad gso: type: 1, size: 1448</code> or other network offloading-related errors, this may affect packet capture.
=== Symptoms ===
* Kernel log shows: <code>bad gso: type: 1, size: 1448, max: 1454</code>
* Network interface errors in dmesg
* Packet capture issues or dropped packets
* High CPU usage during packet processing
=== Root Cause ===
Network offloading features (GSO, TSO, GRO) can cause issues with packet capture software. These features optimize network performance by handling packet segmentation in hardware/driver, but can interfere with raw packet capture.
=== Solution ===
Disable network offloading on the capture interface:
<syntaxhighlight lang="bash">
# Check current offloading status
ethtool -k eth0 | grep -E "generic-segmentation|tcp-segmentation|generic-receive"
# Disable GSO (Generic Segmentation Offload)
ethtool -K eth0 gso off
# Disable TSO (TCP Segmentation Offload)
ethtool -K eth0 tso off
# Disable GRO (Generic Receive Offload)
ethtool -K eth0 gro off
# Disable LRO (Large Receive Offload) if available
ethtool -K eth0 lro off
# Verify changes
ethtool -k eth0 | grep -E "segmentation|offload"
</syntaxhighlight>
=== Making Changes Persistent ===
To make these changes survive reboots, add them to a network configuration script:
<syntaxhighlight lang="bash">
# Option 1: Add to /etc/rc.local (if enabled)
echo "ethtool -K eth0 gso off tso off gro off" >> /etc/rc.local
# Option 2: Create a systemd service
cat > /etc/systemd/system/disable-offload.service << EOF
[Unit]
Description=Disable network offloading for packet capture
After=network.target
[Service]
Type=oneshot
ExecStart=/sbin/ethtool -K eth0 gso off tso off gro off
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
EOF
systemctl enable disable-offload.service
</syntaxhighlight>
</syntaxhighlight>


=== Related Information ===
=== Interface Statistics ===
 
* Replace <code>eth0</code> with your actual capture interface name
* These settings may slightly increase CPU usage but improve packet capture reliability
* Virtual environments (VMware, KVM) may require additional VM-level settings
 
== Packet Ordering Issues: Messages Appearing Out of Sequence ==
If SIP messages are displayed out of order in the VoIPmonitor GUI or in downloaded PCAP files, even after syncing the host machine time with NTP, this indicates packets are arriving at the network interface in an incorrect sequence. This is distinct from Wireshark display artifacts covered in the [[FAQ]] section.
 
=== Distinction from Wireshark Display Issues===
Before continuing, verify the issue is NOT a Wireshark display artifact:
 
*'''Wireshark display artifact:''' PCAP files show correct order when TCP sequence analysis is disabled. Solution: Disable "Analyze TCP sequence numbers" in Wireshark Preferences (see [[FAQ]] for details).
 
*'''Actual packet reordering:''' tcpdump on the VoIPmonitor host shows packets arriving out of order at the network interface. Continue with this section.
 
=== Diagnosis: Use tcpdump to Identify Where Reordering Occurs ===
The key diagnostic question is: Are packets arriving out of order at the network interface, or is the reordering occurring in VoIPmonitor's processing?
 
'''Step 1: Capture traffic directly on the network interface:'''
 
Use tcpdump on the VoIPmonitor host to capture packets at the lowest level:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Capture SIP traffic for 30 seconds to a file
# Detailed NIC stats
# Replace eth0 with your sniffing interface
ethtool -S eth0
tcpdump -i eth0 -nn "sip" -w /tmp/direct_interface_capture.pcap
 
# During the capture, make a test call that shows the out-of-order problem
</syntaxhighlight>
 
'''Step 2: Analyze the tcpdump capture for packet ordering:'''


Open the captured file in Wireshark or use tshark to check if timestamps are sequential:
# Watch packet rates
 
<syntaxhighlight lang="bash">
# Display SIP messages with timestamps sorted
tshark -r /tmp/direct_interface_capture.pcap -Y "sip" -T fields -e frame.time_epoch -e sip.Method -e sip.Status-Code | head -50
 
# Analyze sequence numbers for the same call
tshark -r /tmp/direct_interface_capture.pcap -Y "sip && sip.Call-ID == 'YOUR_CALL_ID'" -T fields -e frame.number -e frame.time_epoch -e sip.CSeq -e sip.Method -e sip.Status-Code
</syntaxhighlight>
 
Replace <code>YOUR_CALL_ID</code> with the actual Call-ID from a problematic call (view it in the GUI's CDR → SIP History tab).
 
'''Step 3: Compare tcpdump with downloaded PCAP from GUI:'''
 
<syntaxhighlight lang="bash">
# Download the PCAP for the same problematic call from the GUI
# Save it as: /tmp/gui_download.pcap
 
# Compare timestamps between direct capture and GUI download
tshark -r /tmp/direct_interface_capture.pcap -Y "sip && sip.Call-ID == 'YOUR_CALL_ID'" -T fields -e frame.time_epoch | sort -n > /tmp/direct_timestamps.txt
tshark -r /tmp/gui_download.pcap -Y "sip && sip.Call-ID == 'YOUR_CALL_ID'" -T fields -e frame.time_epoch | sort -n > /tmp/gui_timestamps.txt
 
# Check if both show similar ordering issues
diff /tmp/direct_timestamps.txt /tmp/gui_timestamps.txt
</syntaxhighlight>
 
=== Diagnostic Decision Matrix ===
 
{| class="wikitable" style="background:#e7f3ff; border:1px solid #3366cc;"
|-
! colspan="2" style="background:#3366cc; color: white;" | Packet Ordering Diagnosis
|-
! Observation
! Root Cause & Solution
|-
| '''tcpdump shows packets OUT of order at interface'''
| '''Network-level issue:''' Packets are arriving in wrong order at the network interface. This is usually caused by '''packet bursts'''. Investigate and eliminate packet bursts on the network path (see solution below).
|-
| '''tcpdump shows packets IN order, but GUI shows OUT of order'''
| '''Potential packet burst issue:''' Large bursts may overwhelm the sensor's queue, causing internal buffering and reordering. Consider using a dedicated capture card with internal clock (see solution below).
|-
| '''Both tcpdump and GUI show same out-of-order pattern'''
| '''Network infrastructure issue:''' The reordering is external to VoIPmonitor. The issue lies in the network path between the monitored devices and the sensor. Work with your network administrator.
|}
 
=== Solution: Investigate and Eliminate Packet Bursts ===
 
Packet bursts are the most common cause of genuine out-of-order packet issues. During periods of high network load, multiple packets may arrive nearly simultaneously or with irregular timing, causing the sensor's capture queue to buffer and reorder packets.
 
'''Diagnosing packet bursts:'''
 
<syntaxhighlight lang="bash">
# Monitor interface packet rates in real-time
watch -n 1 'cat /proc/net/dev | grep eth0'
watch -n 1 'cat /proc/net/dev | grep eth0'
# Check for bursty packet arrival pattern
tcpdump -i eth0 -nn "sip" -l | while read line; do
  echo "$(date +%s.%N) $line"
done | tee /tmp/burst_analysis.log
# Analyze the log for irregular timing patterns
# Look for multiple packets with the same timestamp or very close timestamps
</syntaxhighlight>
</syntaxhighlight>


If you see multiple SIP packets with identical or nearly identical timestamps in the burst analysis log, this confirms packet burst issues.
== See Also ==


'''Eliminating packet bursts:'''
* [[Sniffer_configuration]] - Configuration parameter reference
* [[Sniffer_distributed_architecture]] - Client/server deployment
* [[Capture_rules]] - GUI-based recording rules
* [[Sniffing_modes]] - SPAN, ERSPAN, GRE, TZSP setup
* [[Scaling]] - Performance optimization
* [[Database_troubleshooting]] - Database issues
* [[FAQ]] - Common questions and Wireshark display issues


Packet bursts are typically caused by network infrastructure factors:


*'''Switch buffer overflow:''' Network switches have limited buffers. When traffic exceeds capacity, packets are burst-transmitted when buffer space becomes available.


*'''Asymmetric routing:''' Different network paths for request and response packets can cause varying arrival times.


*'''Layer 2 congestion:''' High traffic on VLANs or shared network segments.


Work with your network administrator to:
* Implement traffic shaping/policing on the monitored network segments
* Increase switch buffer sizes or use switches with larger buffers
* Use quality of service (QoS) to prioritize SIP traffic
* Check for spanning tree topology changes or link flapping on switch ports


=== Solution: Use Dedicated Capture Card with Internal Clock ===
If packet bursts cannot be eliminated from the network or continue despite optimization, using a dedicated network interface card (NIC) with hardware timestamping capabilities can provide accurate packet ordering independent of host system timing issues.


Dedicated capture cards (such as Napatech SmartNICs or similar hardware) provide:


*'''Internal clock:''' The capture card maintains its own precise timing source, independent of the host system clock.
== AI Summary for RAG ==


*'''Hardware timestamping:''' Packets are timestamped as they enter the NIC hardware, before any operating system processing or queuing.
<!-- This section is for AI/RAG systems. Do not edit manually. -->


*'''Large hardware buffers:** Specialized cards have dedicated packet buffers that can absorb bursts without affecting timestamp accuracy.
=== Summary ===
 
Comprehensive troubleshooting guide for VoIPmonitor sniffer/sensor problems. Covers: verifying traffic reaches interface (tcpdump/tshark), diagnosing no calls recorded (service, config, capture rules, SPAN), missing audio/RTP issues (one-way audio, NAT, natalias, rtp_check_both_sides_by_sdp), PACKETBUFFER FULL errors (I/O vs CPU bottleneck diagnosis using syslog metrics heap/t0CPU/SQLq and Linux tools iostat/iotop/ioping), manager commands for thread monitoring (sniffer_threads via socket or port 5029), t0 single-core capture limit and solutions (DPDK/Napatech kernel bypass), I/O solutions (NVMe/SSD, async writes, pcap_dump_writethreads), CPU solutions (max_buffer_mem 10GB+, jitterbuffer tuning), OOM issues (MySQL buffer pool, voipmonitor buffers), network interface problems (promiscuous mode, drops, offloading), packet ordering, database issues (SQL queue, Error 1062).
For VoIPmonitor integration with capture cards, see [[Napatech]] for Napatech-specific configuration and [[Sniffing_modes]] for other hardware-accelerated capture options.
 
=== Workflow Summary ===
 
1. Ensure host time is synced with NTP (step you have already completed)
2. Use tcpdump to capture directly on the interface during a problematic call
3. Analyze the capture to determine if packets are arriving out of order at the network level
4. If tcpdump confirms out-of-order packets:
  * Investigate and eliminate packet bursts in the network infrastructure
  * Consider using dedicated capture cards with internal clock for timestamp accuracy
5. If tcpdump shows packets in order but VoIPmonitor shows out of order:
  * Review PACKETBUFFER settings ([[#Step_8:_PACKETBUFFER_Saturation_Under_High_Load|PACKETBUFFER Saturation]])
  * Consider hardware capture cards for improved timing accuracy
 
{{Note|Do not confuse genuine packet reordering with Wireshark display artifacts. If Wireshark correctly shows packets after disabling TCP sequence analysis, the issue is a display setting, not actual packet ordering.}}
 
== See Also ==
* [[Sniffer_configuration]] - Complete configuration reference for voipmonitor.conf
* [[Sniffer_distributed_architecture]] - Client/server deployment and troubleshooting
* [[Capture_rules]] - GUI-based selective recording configuration
* [[Sniffing_modes]] - Traffic forwarding methods (SPAN, ERSPAN, GRE, TZSP)
* [[Scaling]] - Performance tuning and optimization
* [[Upgrade_to_bigint]] - Migrating CDR table to BIGINT (unrelated to lookup table issues)
* [[FAQ]] - Wireshark display artifacts and out-of-order packet display issues
 
== AI Summary for RAG ==
 
'''Summary:''' Comprehensive troubleshooting guide for VoIPmonitor sensor issues. Key diagnostic flow: (1) Check service status with systemctl, (2) Verify traffic with tshark -i eth0 -Y "sip || rtp", (3) Check SPAN/network configuration including interface drops and asymmetric mirroring, (4) Verify voipmonitor.conf (interface, sipport, filter), (5) Check GUI capture rules for Skip, (6) Review logs for OOM/PACKETBUFFER errors. PACKETBUFFER saturation: "PACKETBUFFER: memory is FULL" errors, truncated RTP - fix with rtpthreads_start=8, max_buffer_mem=13000, threading_expanded=yes. Storage failure: sensor disconnected (red X) with DROPPED PACKETS at low traffic - use smartctl to diagnose, replace disk. EtherChannel/bonded interfaces: false packet loss when monitoring br0/bond0 - use comma-separated physical interfaces instead. OOM scenarios: MySQL killed (tune innodb), voipmonitor killed (reduce buffers), runaway processes (identify with ps aux, kill orphaned). Other issues covered: snaplen truncation, Kamailio siptrace truncation, asymmetric mirroring, rtp_check_both_sides_by_sdp one-way RTP, SQL queue overload, packet ordering issues.


'''Keywords:''' troubleshooting, no calls, PACKETBUFFER, PACKETBUFFER saturation, truncated RTP, rtpthreads_start, max_buffer_mem, storage failure, smartctl, RAID, OOM, tshark, tcpdump, SPAN, RSPAN, ERSPAN, interface, sipport, filter, capture rules, snaplen, Kamailio siptrace, interface drops, asymmetric mirroring, rtp_check_both_sides_by_sdp, one-way RTP, SQL queue, EtherChannel, bonded interface, packet ordering, packet bursts, NTP, time synchronization, promiscuous mode
=== Keywords ===
troubleshooting, sniffer, sensor, no calls, missing audio, one-way audio, RTP, PACKETBUFFER FULL, memory is FULL, buffer saturation, I/O bottleneck, CPU bottleneck, heap, t0CPU, t1CPU, t2CPU, SQLq, comp, tacCPU, iostat, iotop, ioping, sniffer_threads, manager socket, port 5029, thread CPU, t0 thread, single-core limit, DPDK, Napatech, kernel bypass, NVMe, SSD, async write, pcap_dump_writethreads, tar_maxthreads, max_buffer_mem, jitterbuffer, interface_ip_filter, OOM, out of memory, innodb_buffer_pool_size, promiscuous mode, interface drops, ethtool, packet ordering, SPAN, mirror, SQL queue, Error 1062, natalias, NAT, id_sensor, snaplen, capture rules, tcpdump, tshark


'''Key Questions:'''
=== Key Questions ===
* Why is VoIPmonitor not recording any calls?
* Why are no calls being recorded in VoIPmonitor?
* How do I verify SIP/RTP traffic is reaching the sensor?
* How to diagnose PACKETBUFFER FULL or memory is FULL error?
* What causes PACKETBUFFER saturation and how do I fix it?
* How to determine if bottleneck is I/O or CPU?
* How do I distinguish PACKETBUFFER saturation from storage hardware failure?
* What do heap values in syslog mean?
* How do I use smartctl to check disk health?
* What does t0CPU percentage indicate?
* What are symptoms of interface packet drops?
* How to use sniffer_threads manager command?
* How do I check for asymmetric traffic mirroring?
* How to connect to manager socket or port 5029?
* What causes one-way RTP capture?
* What to do when t0 thread is at 100%?
* How do I fix SPAN configured for one direction only?
* How to fix one-way audio or missing RTP?
* What should I verify after server reboot?
* How to configure natalias for NAT?
* Why is time sync critical for packetbuffer_sender?
* How to increase max_buffer_mem for high traffic?
* How do I fix SQL queue overload causing coredumps?
* How to disable jitterbuffer to save CPU?
* Which package is commonly missing on new sensors?
* What causes OOM kills of voipmonitor or MySQL?
* Do I need promiscuous mode for ERSPAN/GRE tunnels?
* How to check disk I/O performance with iostat?
* Why does port-based tcpdump filter miss fragmented SIP packets?
* How to enable promiscuous mode on interface?
* How do I fix OOM caused by runaway external processes?
* How to fix packet ordering issues with SPAN?
* Why does VoIPmonitor report false packet loss on EtherChannel/bonded interfaces?
* What is Error 1062 duplicate entry?
* How do I diagnose and fix out-of-order packet issues?
* How to verify traffic reaches capture interface?

Latest revision as of 19:08, 22 January 2026

Sniffer Troubleshooting

This page covers common VoIPmonitor sniffer/sensor problems organized by symptom. For configuration reference, see Sniffer_configuration. For performance tuning, see Scaling.

Critical First Step: Is Traffic Reaching the Interface?

⚠️ Warning: Before any sensor tuning, verify packets are reaching the network interface. If packets aren't there, no amount of sensor configuration will help. 

# Check for SIP traffic on the capture interface
tcpdump -i eth0 -nn "host <PROBLEMATIC_IP> and port 5060" -c 10

# If no packets: Network/SPAN issue - contact network admin
# If packets visible: Proceed with sensor troubleshooting below

Quick Diagnostic Checklist

Check Command Expected Result
Service running systemctl status voipmonitor Active (running)
Traffic on interface tshark -i eth0 -c 5 -Y "sip" SIP packets displayed
Interface errors ip -s link show eth0 No RX errors/drops
Promiscuous mode ip link show eth0 PROMISC flag present
Logs grep voip No critical errors
GUI rules Settings → Capture Rules No unexpected "Skip" rules

No Calls Being Recorded

Service Not Running

# Check status
systemctl status voipmonitor

# View recent logs
journalctl -u voipmonitor --since "10 minutes ago"

# Start/restart
systemctl restart voipmonitor

Common startup failures:

  • Interface not found: Check interface in voipmonitor.conf matches ip a output
  • Port already in use: Another process using the management port
  • License issue: Check License for activation problems

Wrong Interface or Port Configuration

# Check current config
grep -E "^interface|^sipport" /etc/voipmonitor.conf

# Example correct config:
# interface = eth0
# sipport = 5060

💡 Tip:

GUI Capture Rules Blocking

Navigate to Settings → Capture Rules and check for rules with action "Skip" that may be blocking calls. Rules are processed in order - a Skip rule early in the list will block matching calls.

See Capture_rules for detailed configuration.

SPAN/Mirror Not Configured

If tcpdump shows no traffic:

  1. Verify switch SPAN/mirror port configuration
  2. Check that both directions (ingress + egress) are mirrored
  3. Confirm VLAN tagging is preserved if needed
  4. Test physical connectivity (cable, port status)

See Sniffing_modes for SPAN, RSPAN, and ERSPAN configuration.

Filter Parameter Too Restrictive

If filter is set in voipmonitor.conf, it may exclude traffic: 

# Check filter
grep "^filter" /etc/voipmonitor.conf

# Temporarily disable to test
# Comment out the filter line and restart


Missing id_sensor Parameter

Symptom: SIP packets visible in Capture/PCAP section but missing from CDR, SIP messages, and Call flow.

Cause: The id_sensor parameter is not configured or is missing. This parameter is required to associate captured packets with the CDR database.

Solution: 

# Check if id_sensor is set
grep "^id_sensor" /etc/voipmonitor.conf

# Add or correct the parameter
echo "id_sensor = 1" >> /etc/voipmonitor.conf

# Restart the service
systemctl restart voipmonitor

💡 Tip: Use a unique numeric identifier (1-65535) for each sensor. Essential for multi-sensor deployments. See id_sensor documentation.

Missing Audio / RTP Issues

One-Way Audio (Asymmetric Mirroring)

Symptom: SIP recorded but only one RTP direction captured.

Cause: SPAN port configured for only one direction.

Diagnosis: 

# Count RTP packets per direction
tshark -i eth0 -Y "rtp" -T fields -e ip.src -e ip.dst | sort | uniq -c

If one direction shows 0 or very few packets, configure the switch to mirror both ingress and egress traffic.

RTP Not Associated with Call

Symptom: Audio plays in sniffer but not in GUI, or RTP listed under wrong call.

Possible causes:

1. SIP and RTP on different interfaces/VLANs: 

# voipmonitor.conf - enable automatic RTP association
auto_enable_use_blocks = yes

2. NAT not configured: 

# voipmonitor.conf - for NAT scenarios
natalias = <public_ip> <private_ip>

# If not working, try reversed order:
natalias = <private_ip> <public_ip>

3. External device modifying media ports:

If SDP advertises one port but RTP arrives on different port (SBC/media server issue): 

# Compare SDP ports vs actual RTP
tshark -r call.pcap -Y "sip.Method == INVITE" -V | grep "m=audio"
tshark -r call.pcap -Y "rtp" -T fields -e udp.dstport | sort -u

If ports don't match, the external device must be configured to preserve SDP ports - VoIPmonitor cannot compensate.

RTP Incorrectly Associated with Wrong Call (PBX Port Reuse)

Symptom: RTP streams from one call appear associated with a different CDR when your PBX aggressively reuses the same IP:port across multiple calls.

Cause: When PBX reuses media ports, VoIPmonitor may incorrectly correlate RTP packets to the wrong call based on weaker correlation methods.

Solution: Enable rtp_check_both_sides_by_sdp to require verification of both source and destination IP:port against SDP: 

# voipmonitor.conf - require both source and destination to match SDP
rtp_check_both_sides_by_sdp = yes

# Alternative (strict) mode - allows initial unverified packets
rtp_check_both_sides_by_sdp = strict

⚠️ Warning: Enabling this may prevent RTP association for calls using NAT, as the source IP:port will not match the SDP. Use natalias mappings or the strict setting to mitigate this.

Snaplen Truncation

Symptom: Large SIP messages truncated, incomplete headers.

Solution: 

# voipmonitor.conf - increase packet capture size
snaplen = 8192

For Kamailio siptrace, also check trace_msg_fragment_size in Kamailio config. See snaplen documentation.

PACKETBUFFER Saturation

Symptom: Log shows PACKETBUFFER: memory is FULL, truncated RTP recordings.

⚠️ Warning: This alert refers to VoIPmonitor's internal packet buffer (max_buffer_mem), NOT system RAM. High system memory availability does not prevent this error. The root cause is always a downstream bottleneck (disk I/O or CPU) preventing packets from being processed fast enough.

Before testing solutions, gather diagnostic data:

  • Check sensor logs: /var/log/syslog (Debian/Ubuntu) or /var/log/messages (RHEL/CentOS)
  • Generate debug log via GUI: Tools → Generate debug log

Diagnose: I/O vs CPU Bottleneck

⚠️ Warning: Do not guess the bottleneck source. Use proper diagnostics first to identify whether the issue is disk I/O, CPU, or database-related. Disabling storage as a test is valid but should be used to confirm findings, not as the primary diagnostic method.

Step 1: Check IO[] Metrics (v2026.01.3+)

Starting with version 2026.01.3, VoIPmonitor includes built-in disk I/O monitoring that directly shows disk saturation status: 

[283.4/283.4Mb/s] IO[B1.1|L0.7|U45|C75|W125|R10|WI1.2k|RI0.5k]

Quick interpretation:

Metric Meaning Problem Indicator
C (Capacity) % of disk's sustainable throughput used C ≥ 80% = Warning, C ≥ 95% = Saturated
L (Latency) Current write latency in ms L ≥ 3× B (baseline) = Saturated
U (Utilization) % time disk is busy U > 90% = Disk at limit

If you see DISK_SAT or WARN after IO[]: 

IO[B1.1|L8.5|U98|C97|W890|R5|WI12.5k|RI0.1k] DISK_SAT

→ This confirms I/O bottleneck. Skip to I/O Bottleneck Solutions.

For older versions or additional confirmation, continue with the steps below.

ℹ️ Note: See Syslog Status Line - IO[] section for detailed field descriptions.

Step 2: Read the Full Syslog Status Line

VoIPmonitor outputs a status line every 10 seconds. This is your first diagnostic tool: 

# Monitor in real-time
journalctl -u voipmonitor -f
# or
tail -f /var/log/syslog | grep voipmonitor

Example status line: 

calls[424] PS[C:4 S:41 R:13540] SQLq[C:0 M:0] heap[45|30|20] comp[48] [25.6Mb/s] t0CPU[85%] t1CPU[12%] t2CPU[8%] tacCPU[8|8|7|7%] RSS/VSZ[365|1640]MB

Key metrics for bottleneck identification:

Metric What It Indicates I/O Bottleneck Sign CPU Bottleneck Sign
heap[A|B|C] Buffer fill % (primary / secondary / processing) High A with low t0CPU High A with high t0CPU
t0CPU[X%] Packet capture thread (single-core, cannot parallelize) Low (<50%) High (>80%)
comp[X] Active compression threads Very high (maxed out) Normal
SQLq[C:X M:Y] Pending SQL queries Growing = database bottleneck Stable
tacCPU[...] TAR compression threads All near 100% = compression bottleneck Normal

Interpretation flowchart:

Step 3: Linux I/O Diagnostics

Use these standard Linux tools to confirm I/O bottleneck:

Install required tools: 

# Debian/Ubuntu
apt install sysstat iotop ioping

# CentOS/RHEL
yum install sysstat iotop ioping

2a) iostat - Disk utilization and wait times 

# Run for 10 intervals of 2 seconds
iostat -xz 2 10

Key output columns: 

Device   r/s     w/s   rkB/s   wkB/s  await  %util
sda     12.50  245.30  50.00  1962.40  45.23  98.50
Column Description Problem Indicator
%util Device utilization percentage > 90% = disk saturated
await Average I/O wait time (ms) > 20ms for SSD, > 50ms for HDD = high latency
w/s Writes per second Compare with disk's rated IOPS

2b) iotop - Per-process I/O usage 

# Show I/O by process (run as root)
iotop -o

Look for voipmonitor or mysqld dominating I/O. If voipmonitor shows high DISK WRITE but system %util is 100%, disk cannot keep up.

2c) ioping - Quick latency check 

# Test latency on VoIPmonitor spool directory
cd /var/spool/voipmonitor
ioping -c 20 .

Expected results:

Storage Type Healthy Latency Problem Indicator
NVMe SSD < 0.5 ms > 2 ms
SATA SSD < 1 ms > 5 ms
HDD (7200 RPM) < 10 ms > 30 ms

Step 4: Linux CPU Diagnostics

3a) top - Overall CPU usage 

# Press '1' to show per-core CPU
top

Look for:

  • Individual CPU core at 100% (t0 thread is single-threaded)
  • High %wa (I/O wait) vs high %us/%sy (CPU-bound)

3b) Verify voipmonitor threads 

# Show voipmonitor threads with CPU usage
top -H -p $(pgrep voipmonitor)

If one thread shows ~100% CPU while others are low, you have a CPU bottleneck on the capture thread (t0).

Step 5: Decision Matrix

Observation Likely Cause Go To
heap high, t0CPU > 80%, iostat %util low CPU Bottleneck CPU Solution
heap high, t0CPU < 50%, iostat %util > 90% I/O Bottleneck I/O Solution
heap high, t0CPU < 50%, iostat %util < 50%, SQLq growing Database Bottleneck Database Solution
heap normal, comp maxed, tacCPU all ~100% Compression Bottleneck (type of I/O) I/O Solution

Step 6: Confirmation Test (Optional)

After identifying the likely cause with the tools above, you can confirm with a storage disable test: 

# /etc/voipmonitor.conf - temporarily disable all storage
savesip = no
savertp = no
savertcp = no
savegraph = no

systemctl restart voipmonitor
# Monitor for 5-10 minutes during peak traffic
journalctl -u voipmonitor -f | grep heap
  • If heap values drop to near zero → confirms I/O bottleneck
  • If heap values remain high → confirms CPU bottleneck

⚠️ Warning: Remember to re-enable storage after testing! This test causes call recordings to be lost.

Solution: I/O Bottleneck

ℹ️ Note: If you see IO[...] DISK_SAT or WARN in the syslog status line (v2026.01.3+), disk saturation is already confirmed. See IO[] Metrics for details.

Quick confirmation (for older versions):

Temporarily save only RTP headers to reduce disk write load: 

# /etc/voipmonitor.conf
savertp = header

Restart the sniffer and monitor. If heap usage stabilizes and "MEMORY IS FULL" errors stop, the issue is confirmed to be storage I/O.

Check storage health before upgrading: 

# Check drive health
smartctl -a /dev/sda

# Check for I/O errors in system logs
dmesg | grep -i "i/o error\|sd.*error\|ata.*error"

Look for reallocated sectors, pending sectors, or I/O errors. Replace failing drives before considering upgrades.

Storage controller cache settings:

Storage Type Recommended Cache Mode
HDD / NAS WriteBack (requires battery-backed cache)
SSD WriteThrough (or WriteBack with power loss protection)

Use vendor-specific tools to configure cache policy (megacli, ssacli, perccli).

Storage upgrades (in order of effectiveness):

Solution IOPS Improvement Notes
NVMe SSD 50-100x vs HDD Best option, handles 10,000+ concurrent calls
SATA SSD 20-50x vs HDD Good option, handles 5,000+ concurrent calls
RAID 10 with BBU 5-10x vs single disk Enable WriteBack cache (requires battery backup)
Separate storage server Variable Use client/server mode

Filesystem tuning (ext4): 

# Check current mount options
mount | grep voipmonitor

# Recommended mount options for /var/spool/voipmonitor
# Add to /etc/fstab: noatime,data=writeback,barrier=0
# WARNING: barrier=0 requires battery-backed RAID

Verify improvement: 

# After changes, monitor iostat
iostat -xz 2 10
# %util should drop below 70%, await should decrease

Solution: CPU Bottleneck

Identify CPU Bottleneck Using Manager Commands

VoIPmonitor provides manager commands to monitor thread CPU usage in real-time. This is essential for identifying which thread is saturated.

Connect to manager interface: 

# Via Unix socket (local, recommended)
echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket

# Via TCP port 5029 (remote or local)
echo 'sniffer_threads' | nc 127.0.0.1 5029

# Monitor continuously (every 2 seconds)
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket"

ℹ️ Note: TCP port 5029 is encrypted by default. For unencrypted access, set manager_enable_unencrypted = yes in voipmonitor.conf (security risk on public networks).

Example output: 

t0 - binlog1 fifo pcap read          (  12345) :  78.5  FIFO  99     1234
t2 - binlog1 pb write                (  12346) :  12.3               456
rtp thread binlog1 binlog1 0         (  12347) :   8.1               234
rtp thread binlog1 binlog1 1         (  12348) :   6.2               198
t1 - binlog1 call processing         (  12349) :   4.5               567
tar binlog1 compression 0            (  12350) :   3.2                89

Column interpretation:

Column Description
Thread name Descriptive name (t0=capture, t1=call processing, t2=packet buffer write)
(TID) Linux thread ID (useful for top -H -p TID)
CPU % Current CPU usage percentage - key metric
Sched Scheduler type (FIFO = real-time, empty = normal)
Priority Thread priority
CS/s Context switches per second

Critical threads to watch:

Thread Role If at 90-100%
t0 (pcap read) Packet capture from NIC Single-core limit reached! Cannot parallelize. Need DPDK/Napatech.
t2 (pb write) Packet buffer processing Processing bottleneck. Check t2CPU breakdown.
rtp thread RTP packet processing Threads auto-scale. If still saturated, consider DPDK/Napatech.
tar compression PCAP archiving I/O bottleneck (compression waiting for disk)
mysql store Database writes Database bottleneck. Check SQLq metric.

⚠️ Warning: If t0 thread is at 90-100%, you have hit the fundamental single-core capture limit. The t0 thread reads packets from the kernel and cannot be parallelized. Disabling features like jitterbuffer will NOT help - those run on different threads. The only solutions are:

  • Reduce captured traffic using interface_ip_filter or BPF filter
  • Use kernel bypass (DPDK or Napatech) which eliminates kernel overhead entirely

Interpreting t2CPU Detailed Breakdown

The syslog status line shows t2CPU with detailed sub-metrics: 

t2CPU[pb:10/ d:39/ s:24/ e:17/ c:6/ g:6/ r:7/ rm:24/ rh:16/ rd:19/]
Code Function High Value Indicates
pb Packet buffer output Buffer management overhead
d Dispatch Structure creation bottleneck
s SIP parsing Complex/large SIP messages
e Entity lookup Call table lookup overhead
c Call processing Call state machine processing
g Register processing High REGISTER volume
r, rm, rh, rd RTP processing stages High RTP volume (threads auto-scale)

Thread auto-scaling: VoIPmonitor automatically spawns additional threads when load increases:

  • If d > 50% → SIP parsing thread (s) starts
  • If s > 50% → Entity lookup thread (e) starts
  • If e > 50% → Call/register/RTP threads start

Configuration for High Traffic (>10,000 calls/sec)

# /etc/voipmonitor.conf

# Increase buffer to handle processing spikes (value in MB)
# 10000 = 10 GB - can go higher (20000, 30000+) if RAM allows
# Larger buffer absorbs I/O and CPU spikes without packet loss
max_buffer_mem = 10000

# Use IP filter instead of BPF (more efficient)
interface_ip_filter = 10.0.0.0/8
interface_ip_filter = 192.168.0.0/16
# Comment out any 'filter' parameter

CPU Optimizations

# /etc/voipmonitor.conf

# Reduce jitterbuffer calculations to save CPU (keeps MOS-F2 metric)
jitterbuffer_f1 = no
jitterbuffer_f2 = yes
jitterbuffer_adapt = no

# If MOS metrics are not needed at all, disable everything:
# jitterbuffer_f1 = no
# jitterbuffer_f2 = no
# jitterbuffer_adapt = no

Kernel Bypass Solutions (Extreme Loads)

When t0 thread hits 100% on standard NIC, kernel bypass is the only solution:

Solution Type CPU Reduction Use Case
DPDK Open-source ~70% Multi-gigabit on commodity hardware
Napatech Hardware SmartNIC >97% (< 3% at 10Gbit) Extreme performance requirements

Verify Improvement

# Monitor thread CPU after changes
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket | head -10"

# Or monitor syslog
journalctl -u voipmonitor -f
# t0CPU should drop, heap values should stay < 20%

ℹ️ Note: After changes, monitor syslog heap[A|B|C] values - should stay below 20% during peak traffic. See Syslog_Status_Line for detailed metric explanations.

Storage Hardware Failure

Symptom: Sensor shows disconnected (red X) with "DROPPED PACKETS" at low traffic volumes.

Diagnosis: 

# Check disk health
smartctl -a /dev/sda

# Check RAID status (if applicable)
cat /proc/mdstat
mdadm --detail /dev/md0

Look for reallocated sectors, pending sectors, or RAID degraded state. Replace failing disk.

OOM (Out of Memory)

Identify OOM Victim

# Check for OOM kills
dmesg | grep -i "out of memory\|oom\|killed process"
journalctl --since "1 hour ago" | grep -i oom

MySQL Killed by OOM

Reduce InnoDB buffer pool: 

# /etc/mysql/my.cnf
innodb_buffer_pool_size = 2G  # Reduce from default

Voipmonitor Killed by OOM

Reduce buffer sizes in voipmonitor.conf: 

max_buffer_mem = 2000  # Reduce from default
ringbuffer = 50        # Reduce from default

Runaway External Process

# Find memory-hungry processes
ps aux --sort=-%mem | head -20

# Kill orphaned/runaway process
kill -9 <PID>

For servers limited to 16GB RAM or when experiencing repeated MySQL OOM kills: 

# /etc/my.cnf or /etc/mysql/mariadb.conf.d/50-server.cnf
[mysqld]
# On 16GB server: 6GB buffer pool + 6GB MySQL overhead = 12GB total
# Leaves 4GB for OS + GUI, preventing OOM
innodb_buffer_pool_size = 6G

# Enable write buffering (may lose up to 1s of data on crash but reduces memory pressure)
innodb_flush_log_at_trx_commit = 2

Restart MySQL after changes: 

systemctl restart mysql
# or
systemctl restart mariadb

SQL Queue Growth from Non-Call Data

If sip-register, sip-options, or sip-subscribe are enabled, non-call SIP-messages (OPTIONS, REGISTER, SUBSCRIBE, NOTIFY) can accumulate in the database and cause the SQL queue to grow unbounded. This increases MySQL memory usage and leads to OOM kills of mysqld.

⚠️ Warning: Even with reduced innodb_buffer_pool_size, SQL queue will grow indefinitely without cleanup of non-call data.

Solution: Enable automatic cleanup of old non-call data 

# /etc/voipmonitor.conf
# cleandatabase=2555 automatically deletes partitions older than 7 years
# Covers: CDR, register_state, register_failed, and sip_msg (OPTIONS/SUBSCRIBE/NOTIFY)
cleandatabase = 2555

Restart the sniffer after changes: 

systemctl restart voipmonitor

ℹ️ Note: See Data_Cleaning for detailed configuration options and other cleandatabase_* parameters.

Service Startup Failures

Interface No Longer Exists

After OS upgrade, interface names may change (eth0 → ensXXX): 

# Find current interface names
ip a

# Update all config locations
grep -r "interface" /etc/voipmonitor.conf /etc/voipmonitor.conf.d/

# Also check GUI: Settings → Sensors → Configuration

Missing Dependencies

# Install common missing package
apt install libpcap0.8  # Debian/Ubuntu
yum install libpcap     # RHEL/CentOS

Network Interface Issues

Promiscuous Mode

Required for SPAN port monitoring: 

# Enable
ip link set eth0 promisc on

# Verify
ip link show eth0 | grep PROMISC

ℹ️ Note: Promiscuous mode is NOT required for ERSPAN/GRE tunnels where traffic is addressed to the sensor.

Interface Drops

# Check for drops
ip -s link show eth0 | grep -i drop

# If drops present, increase ring buffer
ethtool -G eth0 rx 4096

Bonded/EtherChannel Interfaces

Symptom: False packet loss when monitoring bond0 or br0.

Solution: Monitor physical interfaces, not logical: 

# voipmonitor.conf - use physical interfaces
interface = eth0,eth1

Network Offloading Issues

Symptom: Kernel errors like bad gso: type: 1, size: 1448 

# Disable offloading on capture interface
ethtool -K eth0 gso off tso off gro off lro off

Packet Ordering Issues

If SIP messages appear out of sequence:

First: Rule out Wireshark display artifact - disable "Analyze TCP sequence numbers" in Wireshark. See FAQ.

If genuine reordering: Usually caused by packet bursts in network infrastructure. Use tcpdump to verify packets arrive out of order at the interface. Work with network admin to implement QoS or traffic shaping. For persistent issues, consider dedicated capture card with hardware timestamping (see Napatech).

ℹ️ Note: For out-of-order packets in client/server mode (multiple sniffers), see Sniffer_distributed_architecture for pcap_queue_dequeu_window_length configuration.

Solutions for SPAN/Mirroring Reordering

If packets arrive out of order at the SPAN/mirror port (e.g., 302 responses before INVITE causing "000 no response" errors):

1. Configure switch to preserve packet order: Many switches allow configuring SPAN/mirror ports to maintain packet ordering. Consult your switch documentation for packet ordering guarantees in mirroring configuration.

2. Replace SPAN with TAP or packet broker: Unlike software-based SPAN mirroring, hardware TAPs and packet brokers guarantee packet order. Consider upgrading to a dedicated TAP or packet broker device for mission-critical monitoring.

Database Issues

SQL Queue Overload

Symptom: Growing SQLq metric, potential coredumps. 

# voipmonitor.conf - increase threads
mysqlstore_concat_limit_cdr = 1000
cdr_check_exists_callid = 0

Error 1062 - Lookup Table Limit

Symptom: Duplicate entry '16777215' for key 'PRIMARY'

Quick fix: 

# voipmonitor.conf
cdr_reason_string_enable = no

See Database Troubleshooting for complete solution.

Bad Packet Errors

Symptom: bad packet with ether_type 0xFFFF detected on interface

Diagnosis: 

# Run diagnostic (let run 30-60 seconds, then kill)
voipmonitor --check_bad_ether_type=eth0

# Find and kill the diagnostic process
ps ax | grep voipmonitor
kill -9 <PID>

Causes: corrupted packets, driver issues, VLAN tagging problems. Check ethtool -S eth0 for interface errors.

Useful Diagnostic Commands

tshark Filters for SIP

# All SIP INVITEs
tshark -r capture.pcap -Y "sip.Method == INVITE"

# Find specific phone number
tshark -r capture.pcap -Y 'sip contains "5551234567"'

# Get Call-IDs
tshark -r capture.pcap -Y "sip.Method == INVITE" -T fields -e sip.Call-ID

# SIP errors (4xx, 5xx)
tshark -r capture.pcap -Y "sip.Status-Code >= 400"

Interface Statistics

# Detailed NIC stats
ethtool -S eth0

# Watch packet rates
watch -n 1 'cat /proc/net/dev | grep eth0'

See Also





AI Summary for RAG

Summary

Comprehensive troubleshooting guide for VoIPmonitor sniffer/sensor problems. Covers: verifying traffic reaches interface (tcpdump/tshark), diagnosing no calls recorded (service, config, capture rules, SPAN), missing audio/RTP issues (one-way audio, NAT, natalias, rtp_check_both_sides_by_sdp), PACKETBUFFER FULL errors (I/O vs CPU bottleneck diagnosis using syslog metrics heap/t0CPU/SQLq and Linux tools iostat/iotop/ioping), manager commands for thread monitoring (sniffer_threads via socket or port 5029), t0 single-core capture limit and solutions (DPDK/Napatech kernel bypass), I/O solutions (NVMe/SSD, async writes, pcap_dump_writethreads), CPU solutions (max_buffer_mem 10GB+, jitterbuffer tuning), OOM issues (MySQL buffer pool, voipmonitor buffers), network interface problems (promiscuous mode, drops, offloading), packet ordering, database issues (SQL queue, Error 1062).

Keywords

troubleshooting, sniffer, sensor, no calls, missing audio, one-way audio, RTP, PACKETBUFFER FULL, memory is FULL, buffer saturation, I/O bottleneck, CPU bottleneck, heap, t0CPU, t1CPU, t2CPU, SQLq, comp, tacCPU, iostat, iotop, ioping, sniffer_threads, manager socket, port 5029, thread CPU, t0 thread, single-core limit, DPDK, Napatech, kernel bypass, NVMe, SSD, async write, pcap_dump_writethreads, tar_maxthreads, max_buffer_mem, jitterbuffer, interface_ip_filter, OOM, out of memory, innodb_buffer_pool_size, promiscuous mode, interface drops, ethtool, packet ordering, SPAN, mirror, SQL queue, Error 1062, natalias, NAT, id_sensor, snaplen, capture rules, tcpdump, tshark

Key Questions

  • Why are no calls being recorded in VoIPmonitor?
  • How to diagnose PACKETBUFFER FULL or memory is FULL error?
  • How to determine if bottleneck is I/O or CPU?
  • What do heap values in syslog mean?
  • What does t0CPU percentage indicate?
  • How to use sniffer_threads manager command?
  • How to connect to manager socket or port 5029?
  • What to do when t0 thread is at 100%?
  • How to fix one-way audio or missing RTP?
  • How to configure natalias for NAT?
  • How to increase max_buffer_mem for high traffic?
  • How to disable jitterbuffer to save CPU?
  • What causes OOM kills of voipmonitor or MySQL?
  • How to check disk I/O performance with iostat?
  • How to enable promiscuous mode on interface?
  • How to fix packet ordering issues with SPAN?
  • What is Error 1062 duplicate entry?
  • How to verify traffic reaches capture interface?
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