Sniffer troubleshooting: Difference between revisions

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{{DISPLAYTITLE:Troubleshooting: No Calls Being Sniffed}}
= Sniffer Troubleshooting =


'''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? ==


<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.}}
flowchart TD
    A[No Calls Being Captured] --> B{Step 1: Service Running?}
    B -->|No| B1[systemctl restart voipmonitor]
    B -->|Yes| C{Step 2: Traffic on Interface?<br/>tshark -i eth0 -Y 'sip'}


    C -->|No packets| D[Step 3: Network Issue]
<syntaxhighlight lang="bash">
    D --> D1{Interface UP?}
# Check for SIP traffic on the capture interface
    D1 -->|No| D2[ip link set dev eth0 up]
tcpdump -i eth0 -nn "host <PROBLEMATIC_IP> and port 5060" -c 10
    D1 -->|Yes| D3{SPAN/RSPAN?}
    D3 -->|Yes| D4[Enable promisc mode]
    D3 -->|ERSPAN/GRE/TZSP| D5[Check tunnel config]


    C -->|Packets visible| E[Step 4: VoIPmonitor Config]
# If no packets: Network/SPAN issue - contact network admin
    E --> E1{interface correct?}
# If packets visible: Proceed with sensor troubleshooting below
    E1 -->|No| E2[Fix interface in voipmonitor.conf]
</syntaxhighlight>
    E1 -->|Yes| E3{sipport correct?}
    E3 -->|No| E4[Add port: sipport = 5060,5080]
    E3 -->|Yes| E5{BPF filter blocking?}
    E5 -->|Maybe| E6[Comment out filter directive]


     E5 -->|No| F[Step 5: GUI Capture Rules]
<kroki lang="mermaid">
     F --> F1{Rules with Skip: ON?}
graph TD
     F1 -->|Yes| F2[Remove/modify rules + reload sniffer]
    A[No Calls Recorded] --> B{Packets on interface?<br/>tcpdump -i eth0 port 5060}
     F1 -->|No| G[Step 6: Check Logs]
     B -->|No packets| C[Network Issue]
    C --> C1[Check SPAN/mirror config]
     C --> C2[Verify VLAN tagging]
     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>


    G --> H{OOM Events?}
== Quick Diagnostic Checklist ==
    H -->|Yes| H1[Step 7: Add RAM / tune MySQL]
    H -->|No| I{Large SIP packets?}
    I -->|Yes| I1{External SIP source?<br/>Kamailio/HAProxy mirror}
    I1 -->|No| I2[Increase snaplen in voipmonitor.conf]
    I1 -->|Yes| I3[Fix external source: Kamailio siptrace or HAProxy tee]
    I2 --> I4[If snaplen change fails, recheck with tcpdump -s0]
    I4 --> I1
    I -->|No| J[Contact Support]
</mermaid>


== Post-Reboot Verification Checklist ==
{| class="wikitable"
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.
|-
! Check !! Command !! Expected Result
|-
| Service running || <code>systemctl status voipmonitor</code> || Active (running)
|-
| 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
|}


=== Verify Firewall/Iptables Rules ===
== No Calls Being Recorded ==


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.
=== Service Not Running ===


;1. Check current firewall status:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For systems using iptables
# Check status
iptables -L -n -v
systemctl status voipmonitor


# For systems using firewalld
# View recent logs
firewall-cmd --list-all
journalctl -u voipmonitor --since "10 minutes ago"


# For systems using ufw
# Start/restart
ufw status verbose
systemctl restart voipmonitor
</syntaxhighlight>
</syntaxhighlight>


;2. Verify critical ports are allowed:
Common startup failures:
Ensure the firewall permits traffic on the following VoIPmonitor ports:
* '''Interface not found''': Check <code>interface</code> in voipmonitor.conf matches <code>ip a</code> output
* SIP ports (default: 5060/udp, or your configured sipport values)
* '''Port already in use''': Another process using the management port
* RTP ports (range used by your PBX)
* '''License issue''': Check [[License]] for activation problems
* GUI access (typically: 80/tcp, 443/tcp)
* Sensor management port: 5029/tcp
* Client-Server connection port: 60024/tcp (for distributed setups)


;3. Make firewall rules persistent:
=== Wrong Interface or Port Configuration ===
To prevent firewall rules from being lost after future reboots:


'''For iptables (Debian/Ubuntu):'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Save current rules
# Check current config
iptables-save > /etc/iptables/rules.v4
grep -E "^interface|^sipport" /etc/voipmonitor.conf
# Install persistent package if not present
apt-get install iptables-persistent
</syntaxhighlight>


'''For firewalld (CentOS/RHEL):'''
# Example correct config:
<syntaxhighlight lang="bash">
# interface = eth0
# Runtime rules automatically persist with --permanent flag
# sipport = 5060
firewall-cmd --permanent --add-port=5060/udp
firewall-cmd --permanent --add-port=60024/tcp
firewall-cmd --reload
</syntaxhighlight>
</syntaxhighlight>


=== Verify System Time Synchronization ===
{{Tip|For multiple SIP ports: <code>sipport = 5060,5061,5080</code>}}


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.
=== GUI Capture Rules Blocking ===


;1. Check current NTP/chrony status:
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.
<syntaxhighlight lang="bash">
# For systems using NTP
ntpstat


# For systems using chrony
See [[Capture_rules]] for detailed configuration.
chronyc tracking
</syntaxhighlight>


;2. Verify time synchronization with servers:
=== SPAN/Mirror Not Configured ===
<syntaxhighlight lang="bash">
# For NTP
ntpq -p


# For chrony
If <code>tcpdump</code> shows no traffic:
chronyc sources -v
# Verify switch SPAN/mirror port configuration
</syntaxhighlight>
# Check that both directions (ingress + egress) are mirrored
# Confirm VLAN tagging is preserved if needed
# Test physical connectivity (cable, port status)


'''Expected output:''' Time offset should be minimal (ideally under 100 milliseconds). Large offsets (several seconds) indicate synchronization problems.
See [[Sniffing_modes]] for SPAN, RSPAN, and ERSPAN configuration.


;3. Manual sync if needed (temporary fix):
=== Filter Parameter Too Restrictive ===
<syntaxhighlight lang="bash">
# Force immediate NTP sync
sudo systemctl restart ntp


# For chrony
If <code>filter</code> is set in voipmonitor.conf, it may exclude traffic:
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>).
<syntaxhighlight lang="bash">
# Check filter
grep "^filter" /etc/voipmonitor.conf


;4. Check distributed architecture time sync:
# Temporarily disable to test
In Client-Server mode, ensure all sensors and the central server are synchronized to the same NTP servers:
# Comment out the filter line and restart
 
<syntaxhighlight lang="bash">
# On each sensor and central server
timedatectl status
</syntaxhighlight>
</syntaxhighlight>


Look for: <code>System clock synchronized: yes</code>


If times are not synchronized across distributed components:
* Verify all systems point to the same reliable NTP source
* Check firewall allows UDP port 123 (NTP)
* Ensure timezones are consistent across all systems


'''Troubleshooting time sync issues:'''
==== Missing id_sensor Parameter ====
* 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? ==
'''Symptom''': SIP packets visible in Capture/PCAP section but missing from CDR, SIP messages, and Call flow.
First, confirm that the sensor process is active and loaded the correct configuration file.


;1. Check the service status (for modern systemd 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.
<syntaxhighlight lang="bash">
systemctl status voipmonitor
</syntaxhighlight>
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:
'''Solution''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
ps aux | grep voipmonitor
# Check if id_sensor is set
</syntaxhighlight>
grep "^id_sensor" /etc/voipmonitor.conf
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 ===
# Add or correct the parameter
echo "id_sensor = 1" >> /etc/voipmonitor.conf


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.
# Restart the service
 
systemctl restart voipmonitor
;1. Check the system logs for the specific error message:
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
tail -f /var/log/syslog | grep voipmonitor
 
# For CentOS/RHEL/AlmaLinux or systemd systems
journalctl -u voipmonitor -f
</syntaxhighlight>
</syntaxhighlight>


;2. Common missing packages for sensors:
{{Tip|Use a unique numeric identifier (1-65535) for each sensor. Essential for multi-sensor deployments. See [[Sniffer_configuration#id_sensor|id_sensor documentation]].}}
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.
== Missing Audio / RTP Issues ==


<syntaxhighlight lang="bash">
=== One-Way Audio (Asymmetric Mirroring) ===
# For Debian/Ubuntu
apt-get update && apt-get install rrdtool


# For CentOS/RHEL/AlmaLinux
'''Symptom''': SIP recorded but only one RTP direction captured.
yum install rrdtool
# OR
dnf install rrdtool
</syntaxhighlight>


;3. Other frequently missing dependencies:
'''Cause''': SPAN port configured for only one direction.
If the error references a specific shared library or binary, install it using your package manager. Common examples:
 
* <code>libpcap</code> or <code>libpcap-dev</code>: Packet capture library
* <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:
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:


'''Diagnosis''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
ldd /usr/local/sbin/voipmonitor | grep pcap
# Count RTP packets per direction
tshark -i eth0 -Y "rtp" -T fields -e ip.src -e ip.dst | sort | uniq -c
</syntaxhighlight>
</syntaxhighlight>


If <code>ldd</code> reports "not found," install the missing library using your package manager.
If one direction shows 0 or very few packets, configure the switch to mirror both ingress and egress traffic.


;5. After installing the missing package, restart the sensor service:
=== RTP Not Associated with Call ===
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
systemctl status voipmonitor
</syntaxhighlight>


Verify the service starts successfully and is now <code>Active: active (running)</code>.
'''Symptom''': Audio plays in sniffer but not in GUI, or RTP listed under wrong call.


== Step 2: Is Network Traffic Reaching the Server? ==
'''Possible causes''':
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:
'''1. SIP and RTP on different interfaces/VLANs''':
<syntaxhighlight lang="bash">
<syntaxhighlight lang="ini">
# For Debian/Ubuntu
# voipmonitor.conf - enable automatic RTP association
apt-get update && apt-get install tshark
auto_enable_use_blocks = yes
</syntaxhighlight>


# For CentOS/RHEL/AlmaLinux
'''2. NAT not configured''':
yum install wireshark
<syntaxhighlight lang="ini">
</syntaxhighlight>
# voipmonitor.conf - for NAT scenarios
natalias = <public_ip> <private_ip>


;2. Listen for SIP traffic on the correct interface:
# If not working, try reversed order:
Replace <code>eth0</code> with the interface name you have configured in <code>voipmonitor.conf</code>.
natalias = <private_ip> <public_ip>
<syntaxhighlight lang="bash">
tshark -i eth0 -Y "sip || rtp" -n
</syntaxhighlight>
</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 ==
'''3. External device modifying media ports''':
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:
If SDP advertises one port but RTP arrives on different port (SBC/media server issue):
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">
<syntaxhighlight lang="bash">
ip link set dev eth0 up
# 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
</syntaxhighlight>
</syntaxhighlight>


;2. Check for Promiscuous Mode (for SPAN/RSPAN Mirrored Traffic):
If ports don't match, the external device must be configured to preserve SDP ports - VoIPmonitor cannot compensate.
'''Important:''' Promiscuous mode requirements depend on your traffic mirroring method:
=== 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.


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


* '''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.
'''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">
For SPAN/RSPAN deployments, check the current promiscuous mode status:
# voipmonitor.conf - require both source and destination to match SDP
<syntaxhighlight lang="bash">
rtp_check_both_sides_by_sdp = yes
ip link show eth0
</syntaxhighlight>
Look for the <code>PROMISC</code> flag.


Enable promiscuous mode manually if needed:
# Alternative (strict) mode - allows initial unverified packets
<syntaxhighlight lang="bash">
rtp_check_both_sides_by_sdp = strict
ip link set eth0 promisc on
</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:
{{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 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:
=== Snaplen Truncation ===


=== Step 1: Use tcpdump to Verify Packet Arrival ===
'''Symptom''': Large SIP messages truncated, incomplete headers.


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:
'''Solution''':
 
<syntaxhighlight lang="ini">
<syntaxhighlight lang="bash">
# voipmonitor.conf - increase packet capture size
# Listen for SIP packets from a specific IP during the next high-traffic window
snaplen = 8192
# 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:
For Kamailio siptrace, also check <code>trace_msg_fragment_size</code> in Kamailio config. See [[Sniffer_configuration#snaplen|snaplen documentation]].
* '''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 ===
== PACKETBUFFER Saturation ==


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.
'''Symptom''': Log shows <code>PACKETBUFFER: memory is FULL</code>, truncated RTP recordings.


Key verification points:
{{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.}}


* '''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.
'''Before testing solutions''', gather diagnostic data:
* Check sensor logs: <code>/var/log/syslog</code> (Debian/Ubuntu) or <code>/var/log/messages</code> (RHEL/CentOS)
* Generate debug log via GUI: '''Tools → Generate debug log'''


* '''Check for Bidirectional Mirroring:''' Your SPAN configuration must capture '''BOTH inbound and outbound traffic'''. On most Cisco switches, this requires specifying:
=== Diagnose: I/O vs CPU Bottleneck ===
  <syntaxhighlight lang="bash">
  monitor session 1 source interface GigabitEthernet1/1 both
  </syntaxhighlight>


  Replace <code>both</code> with:
{{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.}}
  * <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.
==== Step 1: Check IO[] Metrics (v2026.01.3+) ====


* '''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:
'''Starting with version 2026.01.3''', VoIPmonitor includes built-in disk I/O monitoring that directly shows disk saturation status:
  ** 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:
<syntaxhighlight lang="text">
  ** Reduce the number of monitored source ports in the SPAN session
[283.4/283.4Mb/s] IO[B1.1|L0.7|U45|C75|W125|R10|WI1.2k|RI0.5k]
  ** Use multiple SPAN sessions if your switch supports it
</syntaxhighlight>
  ** Consider upgrading to a switch with higher SPAN buffer capacity


* '''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.
'''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 detailed instructions on configuring SPAN/ERSPAN/GRE for different network environments, see [[Sniffing_modes]].
'''If you see <code>DISK_SAT</code> or <code>WARN</code> after IO[]:'''
 
<syntaxhighlight lang="text">
=== Step 3: Check for Sensor Resource Bottlenecks ===
IO[B1.1|L8.5|U98|C97|W890|R5|WI12.5k|RI0.1k] DISK_SAT
 
</syntaxhighlight>
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.


* '''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:
→ This confirms I/O bottleneck. Skip to [[#Solution:_I.2FO_Bottleneck|I/O Bottleneck Solutions]].
  ** 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:
'''For older versions or additional confirmation''', continue with the steps below.
  <syntaxhighlight lang="bash">
  grep -i "out of memory\|killed process" /var/log/syslog | tail -20
  </syntaxhighlight>


* '''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>.
{{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.}}


;3. Verify Your SPAN/Mirror/TAP Configuration:
==== Step 2: Read the Full Syslog Status Line ====
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):
VoIPmonitor outputs a status line every 10 seconds. This is your first diagnostic tool:
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">
<syntaxhighlight lang="bash">
# Capture 100 packets of SIP traffic to a pcap file
# Monitor in real-time
tcpdump -i eth0 -c 100 -s0 port 5060 -w /tmp/encapsulation_check.pcap
journalctl -u voipmonitor -f
# or
tail -f /var/log/syslog | grep voipmonitor
</syntaxhighlight>
</syntaxhighlight>


Then analyze the capture to identify encapsulation:
'''Example status line:'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="text">
# Check for VLAN-tagged packets (802.1Q)
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
tshark -r /tmp/encapsulation_check.pcap -Y "vlan"
 
# 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>
</syntaxhighlight>


Identifying encapsulation issues:
'''Key metrics for bottleneck identification:'''
* '''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.
{| class="wikitable"
|-
! Metric !! What It Indicates !! I/O Bottleneck Sign !! CPU Bottleneck Sign
|-
| <code>heap[A&#124;B&#124;C]</code> || Buffer fill % (primary / secondary / processing) || High A with low t0CPU || High A with high t0CPU
|-
| <code>t0CPU[X%]</code> || Packet capture thread (single-core, cannot parallelize) || Low (<50%) || High (>80%)
|-
| <code>comp[X]</code> || Active compression threads || Very high (maxed out) || Normal
|-
| <code>SQLq[C:X M:Y]</code> || Pending SQL queries || Growing = database bottleneck || Stable
|-
| <code>tacCPU[...]</code> || TAR compression threads || All near 100% = compression bottleneck || Normal
|}


* '''VXLAN/TZSP tunnels:''' These specialized tunneling protocols require proper configuration on the sending device. Consult your network device documentation for VoIPmonitor compatibility requirements.
'''Interpretation flowchart:'''


If encapsulation is identified as the issue, review [[Sniffing_modes]] for detailed configuration guidance.
<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]


;3B. Troubleshooting: RTP Streams Not Displayed for Specific Provider:
    C --> C1[Solution: CPU optimization]
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.
    E --> E1[Solution: Faster storage]
    G --> G1[Solution: MySQL tuning]
</kroki>


=== Step 1: Make a Test Call to Reproduce the Issue===
==== Step 3: Linux I/O Diagnostics ====


First, create a controlled test scenario to investigate the specific provider.
Use these standard Linux tools to confirm I/O bottleneck:


* Determine if the issue affects ALL calls from this provider or only some (e.g., specific codecs, call duration, time of day)
'''Install required tools:'''
* Make a test call that reproduces the problem (e.g., from the problematic provider to a test number)
<syntaxhighlight lang="bash">
* Allow the call to establish and run for at least 30-60 seconds to capture meaningful RTP data
# Debian/Ubuntu
apt install sysstat iotop ioping


=== Step 2: Capture Packets on the Sniffing Interface During the Test Call ===
# CentOS/RHEL
 
yum install sysstat iotop ioping
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>


'''2a) iostat - Disk utilization and wait times'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Capture SIP and RTP packets from the specific provider IP during your test call
# Run for 10 intervals of 2 seconds
# Replace eth0 with your interface and 1.2.3.4 with the provider's IP
iostat -xz 2 10
sudo tcpdump -i eth0 -nn "host 1.2.3.4 and (udp port 5060 or (udp[0] & 0x78) == 0x78)" -v
</syntaxhighlight>


# Capture RTP to a file for detailed analysis (recommended)
'''Key output columns:'''
sudo tcpdump -i eth0 -nn "host 1.2.3.4 and rtp" -w /tmp/test_provider_rtp.pcap
<syntaxhighlight lang="text">
Device  r/s    w/s  rkB/s  wkB/s  await  %util
sda    12.50  245.30  50.00  1962.40  45.23  98.50
</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.
{| class="wikitable"
|-
! Column !! Description !! Problem Indicator
|-
| <code>%util</code> || Device utilization percentage || '''> 90%''' = disk saturated
|-
| <code>await</code> || Average I/O wait time (ms) || '''> 20ms''' for SSD, '''> 50ms''' for HDD = high latency
|-
| <code>w/s</code> || Writes per second || Compare with disk's rated IOPS
|}


=== Step 3: Compare Raw Packet Capture with Sensor Output ===
'''2b) iotop - Per-process I/O usage'''
<syntaxhighlight lang="bash">
# Show I/O by process (run as root)
iotop -o
</syntaxhighlight>


After the test call:
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.


* Check what tcpdump captured:
'''2c) ioping - Quick latency check'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Count SIP packets
# Test latency on VoIPmonitor spool directory
tshark -r /tmp/test_provider_rtp.pcap -Y "sip" | wc -l
cd /var/spool/voipmonitor
 
ioping -c 20 .
# 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>
</syntaxhighlight>


* Check what VoIPmonitor recorded:
'''Expected results:'''
  * Open the CDR for your test call in the GUI
{| class="wikitable"
  * 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
! 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
|}


* Compare the results:
==== Step 4: Linux CPU Diagnostics ====
** '''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:
'''3a) top - Overall CPU usage'''
* [[#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"
<syntaxhighlight lang="bash">
* [[Tls|TLS/SSL Decryption]] - Verify SRTP decryption is configured correctly if the provider uses encryption
# Press '1' to show per-core CPU
* [[Sniffer_configuration]] - Check for any problematic <code>sipport</code> or <code>filter</code> settings
top
</syntaxhighlight>


For more information on capture rules that affect RTP storage, see [[Capture_rules]].
Look for:
* Individual CPU core at 100% (t0 thread is single-threaded)
* High <code>%wa</code> (I/O wait) vs high <code>%us/%sy</code> (CPU-bound)


;5. Check for Non-Call SIP Traffic Only:
'''3b) Verify voipmonitor threads'''
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.
<syntaxhighlight lang="bash">
 
# Show voipmonitor threads with CPU usage
You can configure VoIPmonitor to process and store these non-call SIP messages. See [[SIP_OPTIONS/SUBSCRIBE/NOTIFY]] and [[MESSAGES]] for configuration details.
top -H -p $(pgrep voipmonitor)
 
Enable non-call SIP message processing in '''/etc/voipmonitor.conf''':
<syntaxhighlight lang="ini">
# Process SIP OPTIONS (qualify pings). Default: no
sip-options = yes
 
# 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.
If one thread shows ~100% CPU while others are low, you have a CPU bottleneck on the capture thread (t0).


== Step 4: Check the VoIPmonitor Configuration ==
==== Step 5: Decision Matrix ====
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:
{| class="wikitable"
: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>.
|-
 
! Observation !! Likely Cause !! Go To
;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. For example:
| <code>heap</code> high, <code>t0CPU</code> > 80%, iostat <code>%util</code> low || '''CPU Bottleneck''' || [[#Solution: CPU Bottleneck|CPU Solution]]
:<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
| <code>heap</code> high, <code>t0CPU</code> < 50%, iostat <code>%util</code> > 90% || '''I/O Bottleneck''' || [[#Solution: I/O Bottleneck|I/O Solution]]
|-
|-
| style="vertical-align: top;" | '''Probe side:'''
| <code>heap</code> high, <code>t0CPU</code> < 50%, iostat <code>%util</code> < 50%, <code>SQLq</code> growing || '''Database Bottleneck''' || [[#SQL Queue Overload|Database Solution]]
| 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:'''
| <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]]
| 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:'''
==== Step 6: Confirmation Test (Optional) ====


::1. Verify traffic reachability on the probe:
After identifying the likely cause with the tools above, you can confirm with a storage disable test:
::Use <code>tcpdump</code> on the probe VM to confirm SIP packets for the missing calls are arriving on the expected ports.
::<pre>
::# On the probe VM
::tcpdump -i eth0 -n port 5061
::</pre>


::2. Check the probe's ''voipmonitor.conf'':
<syntaxhighlight lang="ini">
::Ensure the <code>sipport</code> directive on the probe includes all necessary SIP ports used in your network.
# /etc/voipmonitor.conf - temporarily disable all storage
::<syntaxhighlight lang="ini">
savesip = no
::# /etc/voipmonitor.conf on the PROBE
savertp = no
::sipport = 5060,5061,5080,6060
savertcp = no
::</syntaxhighlight>
savegraph = no
</syntaxhighlight>


::3. Check the central analysis host's ''voipmonitor.conf'':
<syntaxhighlight lang="bash">
::'''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.
systemctl restart voipmonitor
::<syntaxhighlight lang="ini">
# Monitor for 5-10 minutes during peak traffic
::# /etc/voipmonitor.conf on the CENTRAL HOST
journalctl -u voipmonitor -f | grep heap
::sipport = 5060,5061,5080,6060
</syntaxhighlight>
::</syntaxhighlight>


::4. Restart both services:
* If <code>heap</code> values drop to near zero → confirms '''I/O bottleneck'''
::Apply the configuration changes:
* If <code>heap</code> values remain high → confirms '''CPU bottleneck'''
::<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]].
{{Warning|Remember to re-enable storage after testing! This test causes call recordings to be lost.}}


;4. Check for a restrictive <code>filter</code>:
=== Solution: I/O Bottleneck ===
: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) ==
{{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.}}
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.
'''Quick confirmation (for older versions):'''


;1. Review existing capture rules:
Temporarily save only RTP headers to reduce disk write load:
:Navigate to '''GUI -> Capture rules''' and examine all rules for any that might be blocking your traffic.
<syntaxhighlight lang="ini">
: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).
# /etc/voipmonitor.conf
savertp = header
</syntaxhighlight>


;2. Test by temporarily removing all capture rules:
Restart the sniffer and monitor. If heap usage stabilizes and "MEMORY IS FULL" errors stop, the issue is confirmed to be storage I/O.
: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:
'''Check storage health before upgrading:'''
:* After restoring your configuration, remove rules one at a time and reload the sniffer after each removal
<syntaxhighlight lang="bash">
:* When calls start being processed again, you have identified the problematic rule
# Check drive health
:* Review the rule's match criteria (IP addresses, prefixes, direction) against your actual traffic pattern
smartctl -a /dev/sda
:* Adjust the rule's conditions or Skip setting as needed


;4. Verify rules are reloaded:
# Check for I/O errors in system logs
: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.
dmesg | grep -i "i/o error\|sd.*error\|ata.*error"
</syntaxhighlight>


For more information on capture rules, see [[Capture_rules]].
Look for reallocated sectors, pending sectors, or I/O errors. Replace failing drives before considering upgrades.


== Step 6: Check VoIPmonitor Logs for Errors ==
'''Storage controller cache settings:'''
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.
{| class="wikitable"
<syntaxhighlight lang="bash">
|-
# For Debian/Ubuntu
! Storage Type !! Recommended Cache Mode
tail -f /var/log/syslog | grep voipmonitor
|-
| HDD / NAS || WriteBack (requires battery-backed cache)
|-
| SSD || WriteThrough (or WriteBack with power loss protection)
|}


# For CentOS/RHEL/AlmaLinux
Use vendor-specific tools to configure cache policy (<code>megacli</code>, <code>ssacli</code>, <code>perccli</code>).
tail -f /var/log/messages | grep voipmonitor
</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 ==
'''Storage upgrades (in order of effectiveness):'''
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.
{| class="wikitable"
|-
! 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 [[Sniffer_distributed_architecture|client/server mode]]
|}


;1. Check for OOM killer events in kernel logs:
'''Filesystem tuning (ext4):'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# For Debian/Ubuntu
# Check current mount options
grep -i "out of memory\|killed process" /var/log/syslog | tail -20
mount | grep voipmonitor


# For CentOS/RHEL/AlmaLinux
# Recommended mount options for /var/spool/voipmonitor
grep -i "out of memory\|killed process" /var/log/messages | tail -20
# Add to /etc/fstab: noatime,data=writeback,barrier=0
 
# WARNING: barrier=0 requires battery-backed RAID
# Also check dmesg:
dmesg | grep -i "killed process" | tail -10
</syntaxhighlight>
</syntaxhighlight>
Typical OOM killer messages look like:
<pre>
Out of memory: Kill process 1234 (mysqld) score 123 or sacrifice child
Killed process 1234 (mysqld) total-vm: 12345678kB, anon-rss: 1234567kB
</pre>


;2. Monitor current memory usage:
'''Verify improvement:'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Check available memory (look for low 'available' or 'free' values)
# After changes, monitor iostat
free -h
iostat -xz 2 10
 
# %util should drop below 70%, await should decrease
# Check per-process memory usage (sorted by RSS)
ps aux --sort=-%mem | head -15
 
# Check MySQL memory usage in bytes
cat /proc/$(pgrep mysqld)/status | grep -E "VmSize|VmRSS"
</syntaxhighlight>
</syntaxhighlight>
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):
=== Solution: CPU Bottleneck ===
* 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


== Step 8: Missing CDRs for Calls with Large Packets ==
==== Identify CPU Bottleneck Using Manager Commands ====
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) ===
VoIPmonitor provides manager commands to monitor thread CPU usage in real-time. This is essential for identifying which thread is saturated.
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:
'''Connect to manager interface:'''
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
grep snaplen /etc/voipmonitor.conf
# Via Unix socket (local, recommended)
</syntaxhighlight>
echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket
Default is 3200 bytes (6000 if SSL/HTTP is enabled).


;2. Test if packet truncation is the issue:
# Via TCP port 5029 (remote or local)
Use <code>tcpdump</code> with <code>-s0</code> (snap infinite) to capture full packets:
echo 'sniffer_threads' | nc 127.0.0.1 5029
<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
# Monitor continuously (every 2 seconds)
tshark -r /tmp/test_capture.pcap -T fields -e frame.len -Y "sip" | sort -n | tail -10
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket"
</syntaxhighlight>
</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">
snaplen = 65535
</syntaxhighlight>
Then restart the sniffer: <code>systemctl restart voipmonitor</code>.


=== Cause 2: MTU Mismatch (Network Infrastructure) ===
{{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).}}
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:
'''Example output:'''
Capture traffic with tcpdump and analyze in Wireshark:
<syntaxhighlight lang="text">
<syntaxhighlight lang="bash">
t0 - binlog1 fifo pcap read          (  12345) :  78.5  FIFO  99    1234
# Capture traffic on the VoIPmonitor host
t2 - binlog1 pb write                (  12346) :  12.3              456
tcpdump -i eth0 -s0 host <pbx_ip_address> -w /tmp/mtu_test.pcap
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>
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:
'''Column interpretation:'''
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.
{| class="wikitable"
|-
! 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
|}
 
'''Critical threads to watch:'''
{| class="wikitable"
|-
! 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.
|}


;3. Identify the MTU bottleneck:
{{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:
The issue is typically a network device with a lower MTU than the end devices. Common locations:
* '''Reduce captured traffic''' using <code>interface_ip_filter</code> or BPF <code>filter</code>
* VPN concentrators
* '''Use kernel bypass''' ([[DPDK]] or [[Napatech]]) which eliminates kernel overhead entirely}}
* 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.
==== Interpreting t2CPU Detailed Breakdown ====


;4. Resolution options:
The syslog status line shows <code>t2CPU</code> with detailed sub-metrics:
* Increase MTU on the bottleneck device to match the rest of the network (e.g., from 1500 to 9000 for jumbo frame environments)
<syntaxhighlight lang="text">
* Enable Path MTU Discovery (PMTUD) on intermediate devices
t2CPU[pb:10/ d:39/ s:24/ e:17/ c:6/ g:6/ r:7/ rm:24/ rh:16/ rd:19/]
* Ensure your switching infrastructure supports jumbo frames end-to-end if you are using them
</syntaxhighlight>


For more information on the <code>snaplen</code> parameter, see [[Sniffer_configuration#Network_Interface_.26_Sniffing|Sniffer Configuration]].
{| class="wikitable"
|-
! 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)
|}


=== Cause 3: External Source Packet Truncation (Traffic Mirroring/LBS Modules) ===
'''Thread auto-scaling:''' VoIPmonitor automatically spawns additional threads when load increases:
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.
* If '''d''' > 50% → SIP parsing thread ('''s''') starts
* If '''s''' > 50% → Entity lookup thread ('''e''') starts
* If '''e''' > 50% → Call/register/RTP threads start


; Symptoms to identify this scenario:
==== Configuration for High Traffic (>10,000 calls/sec) ====
* 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:
<syntaxhighlight lang="ini">
# Kamailio <code>siptrace</code> module
# /etc/voipmonitor.conf
# 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:
# Increase buffer to handle processing spikes (value in MB)
Use <code>tcpdump</code> with <code>-s0</code> (snap infinite) on the VoIPmonitor sensor to compare packet sizes:
# 10000 = 10 GB - can go higher (20000, 30000+) if RAM allows
<syntaxhighlight lang="bash">
# Larger buffer absorbs I/O and CPU spikes without packet loss
# Capture traffic received by VoIPmonitor
max_buffer_mem = 10000
sudo tcpdump -i eth0 -s0 -nn port 5060 -w /tmp/voipmonitor_input.pcap


# Analyze actual packet sizes received
# Use IP filter instead of BPF (more efficient)
tshark -r /tmp/voipmonitor_input.pcap -T fields -e frame.len -Y "sip.Method == INVITE" | sort -n | tail -10
interface_ip_filter = 10.0.0.0/8
interface_ip_filter = 192.168.0.0/16
# Comment out any 'filter' parameter
</syntaxhighlight>
</syntaxhighlight>


If:
==== CPU Optimizations ====
* You see packets with truncated SIP headers or incomplete SDP
* The packet length is much smaller than expected (e.g., 1500 bytes instead of 4000+ bytes)
* Truncation is consistent across all calls


Then the external source is truncating packets before they reach VoIPmonitor.
<syntaxhighlight lang="ini">
 
# /etc/voipmonitor.conf
; 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):
# Reduce jitterbuffer calculations to save CPU (keeps MOS-F2 metric)
<pre>
jitterbuffer_f1 = no
# In kamailio.cfg
jitterbuffer_f2 = yes
modparam("siptrace", "duplicate_uri", "sip:voipmonitor_ip:port;transport=tcp")
jitterbuffer_adapt = no
</pre>


2. If Kamailio reports "Connection refused", VoIPmonitor does not open a TCP listener by default. Manually open one:
# If MOS metrics are not needed at all, disable everything:
<syntaxhighlight lang="bash">
# jitterbuffer_f1 = no
# Open TCP listener using socat
# jitterbuffer_f2 = no
socat TCP-LISTEN:5888,fork,reuseaddr &
# jitterbuffer_adapt = no
</syntaxhighlight>
</syntaxhighlight>
Then update kamailio.cfg to use the specified port instead of the standard SIP port.


3. Use HAProxy traffic 'tee' function (recommended):
==== Kernel Bypass Solutions (Extreme Loads) ====
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:
<pre>
# 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
</pre>


Note: The exact HAProxy configuration depends on your architecture and whether you are mirroring TCP (WebSocket) or UDP traffic.
When t0 thread hits 100% on standard NIC, kernel bypass is the only solution:


; Solutions for other external sources:
{| class="wikitable"
# 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
! Solution !! Type !! CPU Reduction !! Use Case
# 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
| '''[[DPDK]]''' || Open-source || ~70% || Multi-gigabit on commodity hardware
|-
| '''[[Napatech]]''' || Hardware SmartNIC || >97% (< 3% at 10Gbit) || Extreme performance requirements
|}


== Step 9: Probe Timeout Due to Virtualization Timing Issues ==
==== Verify Improvement ====


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.
<syntaxhighlight lang="bash">
# Monitor thread CPU after changes
watch -n 2 "echo 'sniffer_threads' | nc -U /tmp/vm_manager_socket | head -10"


=== Diagnosis: Check System Log Timing Intervals ===
# Or monitor syslog
 
journalctl -u voipmonitor -f
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.
# t0CPU should drop, heap values should stay < 20%
 
;1. Monitor the system log on the affected probe:
<syntaxhighlight lang="bash">
tail -f /var/log/syslog | grep voipmonitor
</syntaxhighlight>
</syntaxhighlight>


;2. Examine the timestamps of voipmonitor status messages:
{{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.}}
Look for repeating log entries that should appear approximately every 10 seconds during normal operations.


;3. Identify timing irregularities:
== Storage Hardware Failure ==
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 ===
'''Symptom''': Sensor shows disconnected (red X) with "DROPPED PACKETS" at low traffic volumes.


This problem is '''not''' network-related. It is a host-level timing issue that impacts the application's internal timers.
'''Diagnosis''':
<syntaxhighlight lang="bash">
# Check disk health
smartctl -a /dev/sda


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


* Irregular system clock behavior on the guest VM
Look for reallocated sectors, pending sectors, or RAID degraded state. Replace failing disk.
* Application timers that do not fire consistently
* Sporadic timeouts in client-server connections


=== Resolution ===
== OOM (Out of Memory) ==


;1. Investigate the virtualization host configuration:
=== Identify OOM Victim ===
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">
<syntaxhighlight lang="bash">
# Monitor for regular status messages
# Check for OOM kills
tail -f /var/log/syslog | grep voipmonitor
dmesg | grep -i "out of memory\|oom\|killed process"
journalctl --since "1 hour ago" | grep -i oom
</syntaxhighlight>
</syntaxhighlight>


Once the timing is corrected, probe connections to the central server should remain stable without intermittent timeouts.
=== MySQL Killed by OOM ===


== Troubleshooting: Audio Missing on One Call Leg ==
Reduce InnoDB buffer pool:
<syntaxhighlight lang="ini">
# /etc/mysql/my.cnf
innodb_buffer_pool_size = 2G  # Reduce from default
</syntaxhighlight>


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.
=== Voipmonitor Killed by OOM ===


The key question to answer is: '''Are the RTP packets for the silent leg present on the wire?'''
Reduce buffer sizes in voipmonitor.conf:
 
<syntaxhighlight lang="ini">
=== Step 1: Use tcpdump to Capture Traffic During a Test Call ===
max_buffer_mem = 2000  # Reduce from default
ringbuffer = 50        # Reduce from default
</syntaxhighlight>


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:
=== Runaway External Process ===


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Capture traffic to a file during the test call
# Find memory-hungry processes
# Replace eth0 with your sniffing interface
ps aux --sort=-%mem | head -20
tcpdump -i eth0 -s0 -w /tmp/direct_capture.pcap


# OR: Display live traffic for specific IPs (useful for real-time diagnostics)
# Kill orphaned/runaway process
tcpdump -i eth0 -s0 -nn "host <pbx_ip> or host <carrier_ip>"
kill -9 <PID>
</syntaxhighlight>
</syntaxhighlight>
For servers limited to '''16GB RAM''' or when experiencing repeated MySQL OOM kills:


Let the call run for 10-30 seconds, then stop tcpdump with Ctrl+C.
<syntaxhighlight lang="ini">
# /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


=== Step 2: Retrieve VoIPmonitor GUI's PCAP for the Same Call ===
# Enable write buffering (may lose up to 1s of data on crash but reduces memory pressure)
 
innodb_flush_log_at_trx_commit = 2
After the call completes:
</syntaxhighlight>
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:


Restart MySQL after changes:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Count RTP packets in the direct capture
systemctl restart mysql
tshark -r /tmp/direct_capture.pcap -Y "rtp" | wc -l
# or
systemctl restart mariadb
</syntaxhighlight>
=== SQL Queue Growth from Non-Call Data ===


# Count RTP packets in the GUI capture
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.
tshark -r /tmp/gui_capture.pcap -Y "rtp" | wc -l


# Check for RTP from specific source IPs in the direct capture
{{Warning|1=Even with reduced <code>innodb_buffer_pool_size</code>, SQL queue will grow indefinitely without cleanup of non-call data.}}
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
'''Solution: Enable automatic cleanup of old non-call data'''
tshark -r /tmp/direct_capture.pcap -Y "sip" -T fields -e sip.Call-ID | head -1
<syntaxhighlight lang="ini">
tshark -r /tmp/gui_capture.pcap -Y "sip" -T fields -e sip.Call-ID | head -1
# /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
</syntaxhighlight>
</syntaxhighlight>


=== Step 4: Interpret the Results ===
Restart the sniffer after changes:
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
</syntaxhighlight>


{| class="wikitable" style="background:#e7f3ff; border:1px solid #3366cc;"
{{Note|See [[Data_Cleaning]] for detailed configuration options and other <code>cleandatabase_*</code> parameters.}}
|-
== Service Startup Failures ==
! 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 ===
=== Interface No Longer Exists ===


;If RTP is NOT on the wire (Network/PBX issue):
After OS upgrade, interface names may change (eth0 → ensXXX):
:* 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):
<syntaxhighlight lang="bash">
:* Configure '''natalias''' in <code>/etc/voipmonitor.conf</code> to map the IP advertised in SIP signaling to the actual RTP source IP:
# Find current interface names
:<syntaxhighlight lang="ini">
ip a
:; /etc/voipmonitor.conf
:natalias = <Public_IP_Signaled> <Private_IP_Actual>
:</syntaxhighlight>
:* '''Critical for NAT scenarios: Ensure <code>rtp_check_both_sides_by_sdp</code> remains at default <code>no</code>'''
:: In NAT environments where only one RTP side is visible, <code>rtp_check_both_sides_by_sdp = no</code> (default) allows matching based on single direction with natalias mapping.
:: Setting <code>rtp_check_both_sides_by_sdp = yes</code> requires BOTH sides to match SDP, which is too strict for NAT scenarios.
:: If you previously enabled <code>rtp_check_both_sides_by_sdp = yes</code> to solve audio mixing issues in multi-call environments, this conflicts with NAT scenarios - keep it at <code>no</code> when using natalias.
:* 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):
# Update all config locations
:* Check CDR view for codec information on both legs
grep -r "interface" /etc/voipmonitor.conf /etc/voipmonitor.conf.d/
:* 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 ===
# Also check GUI: Settings → Sensors → Configuration
</syntaxhighlight>


After making changes in <code>/etc/voipmonitor.conf</code>:
=== Missing Dependencies ===


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Restart the sniffer
# Install common missing package
systemctl restart voipmonitor
apt install libpcap0.8  # Debian/Ubuntu
 
yum install libpcap    # RHEL/CentOS
# 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.
== Network Interface 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.
=== Promiscuous Mode ===


== Troubleshooting: Server Coredumps and SQL Queue Overload ==
Required for SPAN port monitoring:
<syntaxhighlight lang="bash">
# Enable
ip link set eth0 promisc on


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.
# Verify
 
ip link show eth0 | grep PROMISC
=== Symptoms ===
</syntaxhighlight>


* Server crashes or coredumps regularly, often during peak traffic hours
{{Note|Promiscuous mode is NOT required for ERSPAN/GRE tunnels where traffic is addressed to the sensor.}}
* 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 ===
=== Interface Drops ===


;1. Check the SQL queue metric in syslog:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Debian/Ubuntu
# Check for drops
tail -f /var/log/syslog | grep "SQLq"
ip -s link show eth0 | grep -i drop


# CentOS/RHEL
# If drops present, increase ring buffer
tail -f /var/log/messages | grep "SQLq"
ethtool -G eth0 rx 4096
</syntaxhighlight>
</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.
=== Bonded/EtherChannel Interfaces ===


;2. Check if SIP message processing is enabled:
'''Symptom''': False packet loss when monitoring bond0 or br0.
<syntaxhighlight lang="bash">
 
grep -E "sip-options=|sip-subscribe=|sip-notify=" /etc/voipmonitor.conf
'''Solution''': Monitor physical interfaces, not logical:
<syntaxhighlight lang="ini">
# voipmonitor.conf - use physical interfaces
interface = eth0,eth1
</syntaxhighlight>
</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.
=== Network Offloading Issues ===
 
'''Symptom''': Kernel errors like <code>bad gso: type: 1, size: 1448</code>


=== Solutions ===
<syntaxhighlight lang="bash">
# Disable offloading on capture interface
ethtool -K eth0 gso off tso off gro off lro off
</syntaxhighlight>


There are three approaches to resolve SQL queue overload coredumps:
== Packet Ordering Issues ==


==== Solution 1: Increase MySQL Insert Threads ===
If SIP messages appear out of sequence:


Increase the number of threads dedicated to inserting SIP messages into the database. This allows more parallel database operations.
'''First''': Rule out Wireshark display artifact - disable "Analyze TCP sequence numbers" in Wireshark. See [[FAQ]].


Edit <code>/etc/voipmonitor.conf</code> and add or modify:
'''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.}}


<syntaxhighlight lang="ini">
=== Solutions for SPAN/Mirroring Reordering ===
# 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:
If packets arrive out of order at the SPAN/mirror port (e.g., 302 responses before INVITE causing "000 no response" errors):
<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).}}
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.


==== Solution 2: Disable High-Volume SIP Message Types ===
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 ==


Reduce the load on the SQL queue by disabling processing of specific high-volume SIP message types that are not needed for your analysis.
=== SQL Queue Overload ===


Edit <code>/etc/voipmonitor.conf</code>:
'''Symptom''': Growing <code>SQLq</code> metric, potential coredumps.


<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>
</syntaxhighlight>


Restart VoIPmonitor:
=== Error 1062 - Lookup Table Limit ===
<syntaxhighlight lang="bash">
systemctl restart voipmonitor
</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.}}
'''Symptom''': <code>Duplicate entry '16777215' for key 'PRIMARY'</code>


==== Solution 3: Optimize MySQL Performance ===
'''Quick fix''':
<syntaxhighlight lang="ini">
# voipmonitor.conf
cdr_reason_string_enable = no
</syntaxhighlight>


Tune the MySQL/MariaDB server for better write performance to handle the high insert rate from VoIPmonitor.
See [[Database_troubleshooting#Database_Error_1062_-_Lookup_Table_Auto-Increment_Limit|Database Troubleshooting]] for complete solution.


Edit your MySQL configuration file (typically <code>/etc/mysql/my.cnf</code> or <code>/etc/mysql/mariadb.conf.d/50-server.cnf</code>):
== Bad Packet Errors ==


<syntaxhighlight lang="ini">
'''Symptom''': <code>bad packet with ether_type 0xFFFF detected on interface</code>
[mysqld]
# InnoDB buffer pool size - set to approximately 50-70% of available RAM on a dedicated database server
# 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)
'''Diagnosis''':
innodb_flush_log_at_trx_commit = 2
<syntaxhighlight lang="bash">
</syntaxhighlight>
# Run diagnostic (let run 30-60 seconds, then kill)
voipmonitor --check_bad_ether_type=eth0


Restart MySQL and VoIPmonitor:
# Find and kill the diagnostic process
<syntaxhighlight lang="bash">
ps ax | grep voipmonitor
systemctl restart mysql
kill -9 <PID>
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.}}
Causes: corrupted packets, driver issues, VLAN tagging problems. Check <code>ethtool -S eth0</code> for interface errors.
 
=== 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)
== Useful Diagnostic Commands ==
* 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 ==
=== tshark Filters 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">
<syntaxhighlight lang="bash">
# Show all SIP INVITE messages
# All SIP INVITEs
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"
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


# Show SIP and RTP traffic
# SIP errors (4xx, 5xx)
tshark -r capture.pcap -Y "sip || rtp"
tshark -r capture.pcap -Y "sip.Status-Code >= 400"
</syntaxhighlight>
</syntaxhighlight>


=== Search for Specific Phone Number or Text ===
=== Interface Statistics ===
 
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
# Find calls containing a specific phone number (e.g., 5551234567)
# Detailed NIC stats
tshark -r capture.pcap -Y 'sip contains "5551234567"'
ethtool -S eth0


# Find INVITE messages for a specific number
# Watch packet rates
tshark -r capture.pcap -Y 'sip.Method == INVITE && sip contains "5551234567"'
watch -n 1 'cat /proc/net/dev | grep eth0'
</syntaxhighlight>
</syntaxhighlight>


=== Extract Call-ID from Matching Calls ===
== See Also ==
<syntaxhighlight lang="bash">
 
# Get Call-ID for calls matching a phone number
* [[Sniffer_configuration]] - Configuration parameter reference
tshark -r capture.pcap -Y 'sip.Method == INVITE && sip contains "5551234567"' -T fields -e sip.Call-ID
* [[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


# 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
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].
== AI Summary for RAG ==


== See Also ==
<!-- This section is for AI/RAG systems. Do not edit manually. -->
* [[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


== AI Summary for RAG ==
=== Summary ===
'''Summary:''' Comprehensive troubleshooting guide for VoIPmonitor sensor issues. POST-REBOOT VERIFICATION: After planned server reboot, verify two critical items: (1) Firewall/Iptables Rules - check with `iptables -L -n -v`, `firewall-cmd --list-all`, or `ufw status verbose`. Verify VoIPmonitor ports are allowed: SIP (5060/udp), RTP range, GUI (80/tcp, 443/tcp), sensor management (5029/tcp), Client-Server (60024/tcp). Make rules persistent: for iptables use `iptables-save > /etc/iptables/rules.v4` and install `iptables-persistent`; for firewalld use `--permanent` flag. (2) System Time Synchronization - CRITICAL especially for packetbuffer_sender mode. Check with `ntpstat` or `chronyc tracking`. Verify with `ntpq -p` or `chronyc sources -v`. Time offset should be under 100ms. For packetbuffer_sender mode, host and server times must match for proper call correlation (max difference: 2 seconds). Ensure all distributed sensors and central server use same NTP source: `timedatectl status`. Troubleshoot time sync: check firewall allows UDP 123, verify NTP servers reachable, review `/etc/ntp.conf` or `/etc/chrony.conf`, enable service on boot. MAIN TROUBLESHOOTING STEPS for no calls: (1) Verify service running with <code>systemctl status</code>. If service fails to start or crashes immediately with "missing package" error: check logs (syslog/journalctl), install missing dependencies - most commonly <code>rrdtool</code> for RRD graphing/statistics (apt-get install rrdtool or yum/dnf install rrdtool), other common missing packages: libpcap, libssl, zlib. Use <code>ldd</code> to check shared library dependencies. Restart service after installing packages. (2) CRITICAL STEP: Use <code>tshark</code> to verify live traffic is reaching the correct network interface: <code>tshark -i eth0 -Y "sip || rtp" -n</code> (replace eth0 with interface from voipmonitor.conf). If command shows NO packets: issue is network - check SPAN/mirror port configuration on switch, firewall rules. If command shows OPTIONS/NOTIFY/SUBSCRIBE/METHOD but NO INVITE packets: environment has no calls (VOIPmonitor requires INVITE for CDRs). Configure to process non-call SIP messages in voipmonitor.conf with sip-options, sip-message, sip-subscribe, sip-notify set to yes. (3) Check network config - promiscuous mode required for SPAN/RSPAN but NOT for Layer 3 tunnels (ERSPAN/GRE/TZSP/VXLAN). (3A) SPECIAL CASE: Missing packets for specific IPs during high-traffic periods. Use tcpdump FIRST: `tcpdump -i eth0 -nn "host 10.1.2.3 and port 5060"`. If NO packets arrive -> check SPAN config for bidirectional capture (source ports, BOTH inbound/outbound, SPAN buffer saturation during peak, VLAN trunking). If packets DO arrive -> check sensor bottlenecks (ringbuffer, t0CPU, OOM, max_sip_packets_in_call). (3a) If tcpdump shows traffic but VoIPmonitor does NOT capture it, investigate packet encapsulation - capture with tcpdump and analyze with tshark for VLAN tags, ERSPAN, GRE (tshark -Y "gre"), VXLAN (udp.port == 4789), TZSP (udp.port 37008/37009). VLAN tags: ensure filter directive does not use "udp" which drops VLAN-tagged packets. ERSPAN/GRE: verify tunnel configured correctly and packets addressed to sensor IP (promiscuous mode NOT required). VXLAN/TZSP: require proper sending device configuration. (3B) SPECIAL CASE: RTP streams not displayed for specific provider. If SIP signaling works in GUI but RTP streams/quality graphs missing for one provider while working for others: Step 1: Make a test call to reproduce issue. Step 2: During test call, capture RTP packets with tcpdump: `sudo tcpdump -i eth0 -nn "host 1.2.3.4 and rtp" -w /tmp/test_provider_rtp.pcap`. Step 3: Compare tcpdump output with sensor GUI. If tcpdump shows NO RTP packets: network-level issue (asymmetric routing, SPAN config missing RTP path). If tcpdump shows RTP packets but GUI shows no streams: check capture rules with RTP set to DISCARD/Header Only, SRTP decryption config, or sipport/filter settings. (4) Verify <code>voipmonitor.conf</code> settings: interface, sipport, filter directives. (5) Check GUI capture rules with "Skip" option blocking calls. (6) Review system logs for errors. (7) Diagnose OOM killer events causing CDR processing stops. (8) Investigate missing CDRs due tosnaplen truncation, MTU mismatch, or EXTERNAL SOURCE packet truncation. Cause 3: If packets truncated before reaching VoIPmonitor (e.g., Kamailio siptrace, FreeSWITCH sip_trace, custom HEP/HOMER agents, load balancer mirrors), snaplen changes will NOT help. Diagnose with tcpdump -s0; check if received packets smaller than expected. Solutions: For Kamailio siptrace, use TCP transport in duplicate_uri parameter; if connection refused, open TCP listener with socat; best solution: use HAProxy traffic 'tee' to bypass siptrace entirely and send original packets directly. (9) Diagnose probe timeout due to virtualization timing issues - check syslog for 10-second voipmonitor status intervals, RDTSC problems on hypervisor cause >30 second gaps triggering timeouts. (10) Server coredumps and SQL queue overload: Check syslog for growing `SQLq` counter indicating database bottleneck. Symptoms include regular coredumps during peak hours when processing high-volume OPTIONS/SUBSCRIBE/NOTIFY messages. Solutions: 1) Increase `mysqlstore_max_threads_sip_msg` in voipmonitor.conf from default 4 to 8 or higher, restart service. 2) Disable high-volume SIP message types if not needed: set `sip-options=no`, `sip-subscribe=no`, `sip-notify=no`. 3) Optimize MySQL performance with `innodb_buffer_pool_size=8G` (or 50-70% of RAM on dedicated DB, 30-50% on shared) and `innodb_flush_log_at_trx_commit=2`. Restart MySQL and VoIPmonitor after changes. Monitor SQLq metric to verify queue is stable. Includes tshark display filter syntax appendix.
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, no calls, not sniffing, no CDRs, tshark, missing package, missing library, rrdtool, rrdtools, dependencies, service failed, service crashed, ldd, libpcap, libssl, zlib, systemctl restart, journalctl, syslog, promiscuous mode, SPAN, RSPAN, ERSPAN, GRE, TZSP, VXLAN, voipmonitor.conf, interface, sipport, filter, capture rules, Skip, OOM, out of memory, snaplen, MTU, packet truncation, external source truncation, Kamailio siptrace, FreeSWITCH sip_trace, OpenSIPS, HEP, HOMER, HAProxy tee, traffic mirroring, load balancer, socat, TCP listener, WebRTC INVITE, truncated packets, corrupted packets, Authorization header, 4k packets, display filter, sip.Method, sip.Call-ID, probe timeout, virtualization, RDTSC, timing issues, status logs, 10 second interval, KVM, VMware, Hyper-V, Xen, non-call SIP traffic, OPTIONS, NOTIFY, SUBSCRIBE, MESSAGE, sip-options, sip-message, sip-subscribe, sip-notify, qualify pings, heartbeat, instant messaging, encapsulation, packet encapsulation, VLAN tags, 802.1Q, tcpdump analysis, tshark encapsulation filters, high traffic, specific IP, missing packets, specific IP addresses, call legs missing, INVITE missing, high-traffic periods, peak hours, bidirectional capture, inbound outbound, both directions, SPAN buffer saturation, port mirroring, SPAN buffer capacity, rx tx both, monitor session, SPAN source, SPAN destination, ringbuffer, t0CPU, max_sip_packets_in_call, max_invite_packets_in_call, RTP missing, RTP not displayed, RTP missing specific provider, audio quality graphs missing, SRTP, asymmetric routing, RTP test call, tcpdump RTP capture, RTP stream visualization, audio missing, audio missing on one leg, partial audio, silenced audio, one call leg, carrier, PBX, inside, outside, tcpdump tshark comparison, direct capture vs GUI capture, diagnose audio issues, RTP packets on the wire, NAT IP mismatch, natalias configuration, codec issue, transcoding, RTP port configuration, network issue, PBX issue, sniffer configuration, packet correlation, RTP source IP mismatch, SIP signaling IP, coredump, server crash, SQL queue, SQLq, mysqlstore_max_threads_sip_msg, innodb_buffer_pool_size, innodb_flush_log_at_trx_commit, database bottleneck, SQL queue overflow, performance tuning, post-reboot verification, after reboot, server reboot, planned reboot, firewall verification, iptables check, firewalld check, ufw status, firewall persistence, iptables-persistent, firewall persistent, time synchronization, NTP, chrony, ntpstat, chronyc tracking, timedatectl, time sync, time drift, NTP port 123, distributed architecture time sync, client_server_connect_maximum_time_diff_s, packetbuffer_sender time sync
=== 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 ===
* What should I verify after a planned server reboot to ensure VoIPmonitor operates correctly? (Verify firewall rules and time synchronization)
* Why are no calls being recorded in VoIPmonitor?
* How do I check firewall rules after a server reboot? (Use iptables -L -n -v, firewall-cmd --list-all, or ufw status verbose)
* How to diagnose PACKETBUFFER FULL or memory is FULL error?
* Which VoIPmonitor ports should be allowed through the firewall? (SIP: 5060/udp, RTP range, GUI: 80/tcp and 443/tcp, sensor management: 5029/tcp, Client-Server: 60024/tcp)
* How to determine if bottleneck is I/O or CPU?
* How do I make firewall rules persistent across reboots? (For iptables: iptables-save > /etc/iptables/rules.v4 and install iptables-persistent; for firewalld: use --permanent flag)
* What do heap values in syslog mean?
* Why is time synchronization critical for packetbuffer_sender mode? (Host and server times must match for proper call correlation and packet processing; maximum allowed time difference: 2 seconds)
* What does t0CPU percentage indicate?
* How do I check NTP time synchronization after a reboot? (Use ntpstat or chronyc tracking; verify with ntpq -p or chronyc sources -v)
* How to use sniffer_threads manager command?
* How do I ensure all distributed sensors and central server have synchronized time? (Check timedatectl status on each system; ensure they use same NTP source and allow UDP 123)
* How to connect to manager socket or port 5029?
* What is the correct tshark command to verify SIP/RTP traffic is reaching the VoIPmonitor sensor? (Use: tshark -i eth0 -Y "sip || rtp" -n)
* What to do when t0 thread is at 100%?
* How do I diagnose why sniffer captures full audio on one call leg but no audio on the other leg?
* How to fix one-way audio or missing RTP?
* How do I use tcpdump to diagnose missing audio on one call leg?
* How to configure natalias for NAT?
* How do I compare tcpdump capture with the GUI's PCAP file?
* How to increase max_buffer_mem for high traffic?
* How do I determine if RTP packets are on the wire when one leg has no audio?
* How to disable jitterbuffer to save CPU?
* What is the diagnostic workflow for audio missing on one call leg?
* What causes OOM kills of voipmonitor or MySQL?
* How do I determine if audio issue is network/PBX problem vs VoIPmonitor configuration?
* How to check disk I/O performance with iostat?
* How do I check if RTP packets for the silent leg are present on the wire?
* How to enable promiscuous mode on interface?
* How do I verify if natalias is needed for NAT IP mismatch?
* How to fix packet ordering issues with SPAN?
* How do I diagnose whether one-way audio is a codec issue or network issue?
* What is Error 1062 duplicate entry?
* How do I use tcpdump vs GUI PCAP comparison for troubleshooting?
* How to verify traffic reaches capture interface?
* What should I do first when one call leg has missing or partial audio?
* How do I interpret tcpdump vs GUI capture comparison results?
* How do I check for codec/transcoding issues causing one-way audio?
* How do I configure VoIPmonitor to process non-call SIP messages like OPTIONS/NOTIFY/SUBSCRIBE?
* How do I check for VLAN tags in a pcap file?
* How do I detect ERSPAN or GRE tunnels with tshark?
* How do I check for VXLAN encapsulation in my capture?
* How do I identify TZSP packets in a pcap?
* Why does my BPF filter drop VLAN-tagged packets?
* Do I need promiscuous mode for ERSPAN or GRE tunnels?
* Why is VoIPmonitor not recording any calls?
* How can I check if VoIP traffic is reaching my sensor server?
* How do I enable promiscuous mode on my network card?
* What are the most common reasons for VoIPmonitor not capturing data?
* How do I filter tshark output for SIP INVITE messages?
* What is the correct tshark filter syntax to find a specific phone number?
* Why is my VoIPmonitor probe stopping processing calls?
* What does the "Skip" option in capture rules do?
* How do I check for OOM killer events in Linux?
* Why are CDRs missing for calls with large SIP packets?
* What does the snaplen parameter do in voipmonitor.conf?
* Traffic capture stopped with missing package error, what should I do?
* Which package is commonly missing on newly installed sensors?
* How do I fix a missing library dependency for VoIPmonitor sensor?
* How do I diagnose MTU-related packet loss?
* Why are my large SIP packets truncated even after increasing snaplen?
* How do I tell if packets are truncated by VoIPmonitor or by an external source?
* How do I fix Kamailio siptrace truncating large packets?
* What is HAProxy traffic tee and how can it help with packet truncation?
* Why does Kamailio report "Connection refused" when sending siptrace via TCP?
* How do I open a TCP listener on VoIPmonitor for Kamailio siptrace?
* How do I use socat to open a TCP listening port?
* How do I troubleshoot missing packets for specific IP addresses?
* Why are packets missing only during high-traffic periods?
* How do I use tcpdump to verify if packets reach the VoIPmonitor sensor?
* What should I check if tcpdump shows no traffic but the PBX is sending packets?
* How do I verify SPAN configuration is capturing bidirectional traffic?
* What is SPAN buffer saturation and how does it affect packet capture?
* How do I configure Cisco switch SPAN for bidirectional mirroring?
* Why are packets missing for specific IP addresses during peak hours?
* What is the difference between rx, tx, and both in SPAN configuration?
* How do I know if my SPAN buffer is overloading during high traffic?
* Why do some calls work but others miss packet legs for specific IPs?
* How do I verify SPAN source and destination ports are correct?
* How do I check if SPAN is configured for trunk mode on VLAN traffic?
* Do I need SPAN to capture both ingress and egress traffic?
* When should I check SPAN buffer capacity vs sensor t0CPU for packet drops?
* What should I do if FreeSWITCH sip_trace is truncating packets?
* Why are my probes disconnecting from the server with timeout errors?
* How do I diagnose probe timeout issues on high-performance networks?
* What causes intermittent probe timeout errors in client-server mode?
* How do I check for virtualization timing issues on VoIPmonitor probes?
* Why are there no CDRs even though tshark shows SIP OPTIONS/NOTIFY traffic?
* How do I enable sip-options, sip-message, sip-subscribe, sip-notify in voipmonitor.conf?
* What SIP methods are processed to generate CDRs vs non-call records?
* Why are RTP streams not displayed in the GUI for a specific provider?
* How do I use tcpdump to capture RTP packets during a test call?
* How do I diagnose missing RTP audio quality graphs for one provider?
* If SIP signaling works but RTP is missing for a specific provider, what should I check?
* Why is my VoIPmonitor server experiencing regular coredumps?
* How do I check for SQL queue overload causing server crashes?
* What does the SQLq metric in syslog indicate?
* How do I fix server coredumps caused by high-volume OPTIONS/SUBSCRIBE/NOTIFY processing?
* What is the mysqlstore_max_threads_sip_msg parameter and how do I tune it?
* How much should I set mysqlstore_max_threads_sip_msg to for high traffic?
* How do I disable SIP message types that are causing SQL queue overload?
* How do I optimize MySQL performance to prevent SQL queue-related coredumps?
* What is the recommended innodb_buffer_pool_size for VoIPmonitor servers?
* How do I set innodb_flush_log_at_trx_commit for better database write performance?
* What are the trade-offs when setting innodb_flush_log_at_trx_commit to 2?

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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