Sniffer distributed architecture: Difference between revisions

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{{DISPLAYTITLE:Distributed Architecture: Client-Server Mode}}
{{DISPLAYTITLE:Distributed Architecture: Client-Server Mode}}


This guide explains how to deploy multiple VoIPmonitor sensors in a distributed architecture using the modern Client-Server mode.
This guide covers deploying multiple VoIPmonitor sensors in a distributed architecture using Client-Server mode (v20+).


== Overview ==
For deployment options including on-host vs dedicated sensors and traffic forwarding methods (SPAN, GRE, TZSP, VXLAN), see [[Sniffing_modes|VoIPmonitor Deployment & Topology Guide]].


VoIPmonitor v20+ uses a '''Client-Server architecture''' for distributed deployments. Remote sensors connect to a central server via encrypted TCP channel.
= Overview =
 
VoIPmonitor v20+ uses '''Client-Server architecture''' for distributed deployments. Remote sensors connect to a central server via encrypted TCP (default port 60024, zstd compression).


{| class="wikitable"
{| class="wikitable"
|-
|-
! Mode !! What is sent !! Processing location !! Use case
! Mode !! <code>packetbuffer_sender</code> !! What is Sent !! Processing Location !! Use Case
|-
|-
| '''Local Processing''' || CDRs only || Remote sensor || Multiple sites, low bandwidth
| '''Local Processing''' || <code>no</code> (default) || CDRs only || Remote sensor || Multi-site, low bandwidth
|-
|-
| '''Packet Mirroring''' || Raw packets || Central server || Centralized analysis, low-resource remotes
| '''Packet Mirroring''' || <code>yes</code> || Raw packets || Central server || Centralized analysis, low-resource remotes
|}
|}
The mode is controlled by a single option: <code>packetbuffer_sender</code>
For comprehensive deployment options including on-host vs dedicated sensors, traffic forwarding methods (SPAN, GRE, TZSP, VXLAN), and NFS/SSHFS alternatives, see [[Sniffing_modes|VoIPmonitor Deployment & Topology Guide]].
== Client-Server Mode ==
=== Architecture ===


<kroki lang="plantuml">
<kroki lang="plantuml">
Line 49: Line 43:
</kroki>
</kroki>


=== Configuration ===
== Use Cases ==
 
'''AWS VPC Traffic Mirroring Alternative:'''
If experiencing packet loss with AWS VPC Traffic Mirroring (VXLAN overhead, MTU fragmentation), use client-server mode instead:
* Install VoIPmonitor on each source EC2 instance
* Send via encrypted TCP to central server
* Eliminates VXLAN encapsulation and MTU issues
 
= Configuration =
 
== Remote Sensor (Client) ==


'''Remote Sensor (client):'''
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
id_sensor              = 2                    # unique per sensor
id_sensor              = 2                    # Unique per sensor (1-65535)
server_destination      = central.server.ip
server_destination      = central.server.ip
server_destination_port = 60024
server_destination_port = 60024
server_password        = your_strong_password
server_password        = your_strong_password


# Choose one:
# Choose mode:
packetbuffer_sender    = no    # Local Processing: analyze locally, send CDRs
packetbuffer_sender    = no    # Local Processing: analyze locally, send CDRs
# packetbuffer_sender  = yes    # Packet Mirroring: send raw packets
# packetbuffer_sender  = yes    # Packet Mirroring: send raw packets
Line 67: Line 70:
</syntaxhighlight>
</syntaxhighlight>


'''Important: Source IP Binding with <code>manager_ip</code>'''
{{Tip|1=For HA setups with floating IPs, use <code>manager_ip = 10.0.0.5</code> to bind outgoing connections to a static IP address.}}


For remote sensors with multiple IP addresses (e.g., in High Availability setups with a floating/virtual IP), use the <code>manager_ip</code> parameter to bind the outgoing connection to a specific static IP address. This ensures the central server sees a consistent source IP from each sensor, preventing connection issues during failover.
== Central Server ==


<syntaxhighlight lang="ini">
# On sensor with multiple interfaces (e.g., static IP + floating HA IP)
manager_ip              = 10.0.0.5    # Bind to the static IP address
server_destination      = 192.168.1.100
# The outgoing connection will use 10.0.0.5 as the source IP instead of the floating IP
</syntaxhighlight>
Useful scenarios:
* HA pairs: Sensors use static IPs while floating IP is only for failover management
* Multiple VNICs: Explicit source IP selection on systems with multiple virtual interfaces
* Network ACLs: Ensure connections originate from whitelisted IP addresses
'''Central Server:'''
<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
server_bind            = 0.0.0.0
server_bind            = 0.0.0.0
Line 96: Line 86:
# If receiving raw packets (packetbuffer_sender=yes on clients):
# If receiving raw packets (packetbuffer_sender=yes on clients):
sipport                = 5060
sipport                = 5060
# ... other sniffer options
savertp                = yes
savesip                = yes
</syntaxhighlight>
 
{{Warning|1='''Critical:''' Exclude <code>server_bind_port</code> from <code>sipport</code> on the central server. Including it causes continuously increasing memory usage.
<syntaxhighlight lang="ini">
# WRONG - includes sensor communication port:
sipport = 1-65535
 
# CORRECT - excludes port 60024:
sipport = 1-60023,60025-65535
</syntaxhighlight>}}
 
== Key Configuration Rules ==
 
{| class="wikitable"
|-
! Rule !! Applies To !! Why
|-
| <code>server_bind_port</code> must match <code>server_destination_port</code> || Both || Connection fails if mismatched
|-
| <code>sipport</code> must match on probe and central server || Packet Mirroring || Missing ports = missing calls
|-
| <code>natalias</code> only on central server || Packet Mirroring || Prevents RTP correlation issues
|-
| Each sensor needs unique <code>id_sensor</code> || All || Required for identification
|}
 
= Local Processing vs Packet Mirroring =
 
{| class="wikitable"
|-
! !! Local Processing !! Packet Mirroring
|-
| '''<code>packetbuffer_sender</code>''' || <code>no</code> (default) || <code>yes</code>
|-
| '''Processing location''' || Remote sensor || Central server
|-
| '''PCAP storage''' || Remote sensor || Central server
|-
| '''WAN bandwidth''' || Low (CDRs only, 1Gb sufficient) || High (full packets)
|-
| '''Remote CPU load''' || Higher || Minimal
|-
| '''Capture rules applied''' || On sensor || On central server only
|}
 
== PCAP Access in Local Processing Mode ==
 
PCAPs are stored on remote sensors. The GUI retrieves them through the central server, which proxies the request to the sensor '''over the existing TCP/60024 connection''' - the same persistent encrypted channel the sensor uses for sending CDRs. This connection is bidirectional; the central server does not open any separate connection back to the sensor.
 
'''Firewall requirements:'''
 
{| class="wikitable"
|-
! Direction !! Port !! Purpose
|-
| Remote sensors → Central server || TCP/60024 || Persistent encrypted channel (CDRs from sensor, PCAP requests from server - bidirectional)
|-
| GUI → Central server || TCP/5029 || Manager API (sensor status, active calls, configuration)
|-
| GUI → Central server || TCP/60024 || Server API (list connected sensors, proxy PCAP retrieval)
|}
 
{{Note|1=The central server does '''not''' initiate connections to remote sensors. All server↔sensor communication happens over the single TCP/60024 connection that the sensor established.}}
 
{{Tip|1=Packet Mirroring (<code>packetbuffer_sender=yes</code>) '''automatically deduplicates calls''' - the central server merges packets from all probes for the same Call-ID into a single unified CDR. This also ensures one logical call only consumes one license channel.}}
= Advanced Topics =
 
== High Availability (Failover) ==
 
Remote sensors can specify multiple central servers:
 
<syntaxhighlight lang="ini">
server_destination = 192.168.0.1, 192.168.0.2
</syntaxhighlight>
</syntaxhighlight>


=== Custom Port Configuration ===
If primary is unavailable, the sensor automatically connects to the next server.


'''Critical:''' The <code>server_bind_port</code> on the central server must match the <code>server_destination_port</code> on each remote sensor. If these ports do not match, sensors cannot connect.
== Connection Compression ==


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Central Server (listening on custom port 50291)
# On both client and server (default: zstd)
server_type_compress = zstd  # Options: zstd, gzip, lzo, none
</syntaxhighlight>
 
== Intermediate Server (Hub-and-Spoke) ==
 
An intermediate server can receive from multiple sensors and forward to a central server:
 
<kroki lang="plantuml">
@startuml
skinparam shadowing false
skinparam defaultFontName Arial
 
rectangle "Remote Sensors" as RS
rectangle "Intermediate Server" as INT
rectangle "Central Server" as CS
database "MySQL" as DB
 
RS --> INT : TCP/60024
INT --> CS : TCP/60024
CS --> DB
@enduml
</kroki>
 
<syntaxhighlight lang="ini">
# On INTERMEDIATE SERVER
id_sensor              = 100
 
# Receive from remote sensors
server_bind            = 0.0.0.0
server_bind            = 0.0.0.0
server_bind_port        = 50291      # Custom port (default is 60024)
server_bind_port        = 60024
server_password        = your_strong_password
server_password        = sensor_password
 
# Forward to central server
server_destination      = central.server.ip
server_destination_port = 60024
 
packetbuffer_sender    = no    # or yes, depending on desired mode
</syntaxhighlight>
</syntaxhighlight>
{{Note|1=This works because the intermediate server does NOT do local packet capture - it only relays. Original remote sensors must be manually added to GUI Settings for visibility.}}
== Multiple Receivers for Packet Mirroring ==
{{Warning|1=Multiple sensors with <code>packetbuffer_sender=yes</code> sending to a '''single receiver instance''' can cause call processing conflicts (calls appear in Active Calls but missing from CDRs).}}
'''Solution:''' Run separate receiver instances on different hosts, each dedicated to specific sensors:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Remote Sensor (must match the server's custom port)
# Receiver Instance 1 (Host 1, for Sensor A)
server_destination      = 45.249.9.2
server_bind_port        = 60024
server_destination_port = 50291      # MUST match server_bind_port
id_sensor              = 1
server_password        = your_strong_password
 
# Receiver Instance 2 (Host 2, for Sensor B)
server_bind_port       = 60024
id_sensor              = 2
</syntaxhighlight>
</syntaxhighlight>


'''Common reasons to use a custom port:'''
Alternative: Use '''Local Processing mode''' (<code>packetbuffer_sender=no</code>) which processes calls independently on each sensor.


* Firewall restrictions that block the default port 60024
== Preventing Duplicate CDRs (Local Processing) ==
* Running multiple VoIPmonitor instances on the same server (each with a different port)
* Compliance requirements for non-standard ports
* Avoiding port conflicts with other services


''' Troubleshooting Connection Failures: '''
When multiple probes capture the same call in Local Processing mode:


If probes cannot connect to the server:
<syntaxhighlight lang="ini">
# On each probe
cdr_check_exists_callid = yes
</syntaxhighlight>


1. '''Verify ports match on both sides:'''
This checks for existing CDRs before inserting. Requires MySQL UPDATE privileges.
  <syntaxhighlight lang="bash">
  # On central server - check which port it is listening on
  ss -tulpn | grep voipmonitor
  # Should show: voipmonitor LISTEN 0.0.0.0:50291
  </syntaxhighlight>


2. '''Test connectivity from remote sensor:'''
== Critical: SIP and RTP Must Be Captured Together ==
  <syntaxhighlight lang="bash">
  # Test TCP connection to the server's custom port
  nc -zv 45.249.9.2 50291
  # Success: "Connection to 45.249.9.2 50291 port [tcp/*] succeeded!"
  # Timeout/Refused: Check firewall or misconfigured port
  </syntaxhighlight>


3. '''Ensure firewall allows the custom port:'''
VoIPmonitor cannot correlate SIP and RTP from different sniffer instances. A '''single sniffer must process both SIP and RTP''' for each call. Parameters like <code>cdr_check_exists_callid</code> do NOT enable split SIP/RTP correlation.
  <syntaxhighlight lang="bash">
  # Allow inbound TCP on custom port (example for firewalld)
  firewall-cmd --permanent --add-port=50291/tcp
  firewall-cmd --reload
  </syntaxhighlight>


4. '''Check logs on both sides:'''
  <syntaxhighlight lang="bash">
  journalctl -u voipmonitor -f
  # Look for: "connecting to server", "connection refused", or "timeout"
  </syntaxhighlight>


5. '''Verify MySQL database is accessible (if web GUI works but sensors cannot connect):'''
  If the web portal is accessible but sensors cannot connect, verify that the MySQL/MariaDB database service on the primary server is running and responsive. The central VoIPmonitor service requires a functioning database connection to accept sensor data.
  <syntaxhighlight lang="bash">
  # Check if MySQL service is running
  systemctl status mariadb
  # or
  systemctl status mysqld


  # Check for database errors in MySQL error log
==== Split SIP/RTP with Packet Mirroring Mode ====
  # Common locations:
  tail -50 /var/log/mariadb/mariadb.log
  tail -50 /var/log/mysql/error.log
  # Look for critical errors that might prevent database connections
  </syntaxhighlight>


If MySQL is down or experiencing critical errors, the central VoIPmonitor server may not be able to accept sensor connections even though the web interface (PHP) remains accessible. Restart the database service if needed and monitor the logs for recurring errors.
{{Note|1='''Exception for Packet Mirroring Mode:''': The above limitation applies to '''Local Processing mode''' (<code>packetbuffer_sender=no</code>) where each sensor processes calls independently. In '''Packet Mirroring mode''' (<code>packetbuffer_sender=yes</code>), the central server receives raw packets from multiple remote sensors and processes them together. This allows scenarios where SIP and RTP are captured on separate nodes - configure both as packet senders and let the central server correlate them into single unified CDRs.}}


After changing port configuration, restart the service:
Example scenario: Separate SIP signaling node and RTP handling node:
<syntaxhighlight lang="ini">
# SIP Signaling Node (packet sender)
id_sensor              = 1
packetbuffer_sender    = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password        = your_password


<syntaxhighlight lang="bash">
# RTP Handling Node (packet sender)
systemctl restart voipmonitor
id_sensor              = 2
packetbuffer_sender    = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password        = your_password
</syntaxhighlight>
</syntaxhighlight>


=== Connection Compression ===
The central server merges packets from both senders by Call-ID, creating unified CDRs with complete SIP and RTP data.
 
 
==== HEP Protocol in Client/Server Mode ====
 
VoIPmonitor supports receiving HEP-encapsulated traffic on sniffer clients and forwarding it to a central server. This enables distributed capture from HEP sources (Kamailio, OpenSIPS, rtpproxy, FreeSWITCH) in a client/server architecture.


The client-server channel supports compression to reduce bandwidth usage:
'''Scenario:''' SIP proxy and RTP proxy at different locations sending HEP to remote sniffer clients:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# On both client and server (default: zstd)
# Remote Sniffer Client A (receives HEP from Kamailio)
server_type_compress = zstd
id_sensor              = 1
hep                    = yes
hep_bind_port          = 9060
packetbuffer_sender    = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password        = your_password
 
# Remote Sniffer Client B (receives HEP from rtpproxy)
id_sensor              = 2
hep                    = yes
hep_bind_port          = 9060
packetbuffer_sender    = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password        = your_password
</syntaxhighlight>
</syntaxhighlight>


Available options: <code>zstd</code> (default, recommended), <code>gzip</code>, <code>lzo</code>, <code>none</code>
The central server receives packets from both clients and correlates them into unified CDRs using standard SIP Call-ID and IP:port from SDP.
 
{{Note|1=This also works for IPFIX (Oracle SBCs) and RibbonSBC protocols forwarded via client/server mode.}}


=== High Availability (Failover) ===
'''Alternative: Direct HEP to single sniffer'''


Remote sensors can specify multiple central server IPs for automatic failover:
If both HEP sources can reach the same sniffer directly, no client/server setup is needed:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Remote sensor configuration with failover
# Single sniffer receiving HEP from multiple sources
server_destination = 192.168.0.1, 192.168.0.2
hep                    = yes
hep_bind_port          = 9060
interface              = eth0  # Can also sniff locally if needed
</syntaxhighlight>
 
Both Kamailio (SIP) and rtpproxy (RTP) send HEP to this sniffer on port 9060. The sniffer correlates them automatically based on Call-ID and SDP IP:port.
= Sensor Health Monitoring =
 
== Management API ==
 
Query sensor status via TCP port 5029:
 
<syntaxhighlight lang="bash">
echo 'sniffer_stat' | nc <sensor_ip> 5029
</syntaxhighlight>
</syntaxhighlight>


If the primary server becomes unavailable, the sensor automatically connects to the next server in the list.
Returns JSON with status, version, active calls, packets per second, etc.
 
== Multi-Sensor Health Check Script ==
 
<syntaxhighlight lang="bash">
#!/bin/bash
SENSORS=("192.168.1.10:5029" "192.168.1.11:5029")
for SENSOR in "${SENSORS[@]}"; do
    IP=$(echo $SENSOR | cut -d: -f1)
    PORT=$(echo $SENSOR | cut -d: -f2)
    STATUS=$(echo 'sniffer_stat' | nc -w 2 $IP $PORT 2>/dev/null | grep -o '"status":"[^"]*"' | cut -d'"' -f4)
    echo "$IP: ${STATUS:-FAILED}"
done
</syntaxhighlight>


== Local Processing vs Packet Mirroring ==
= Version Compatibility =


{| class="wikitable"
{| class="wikitable"
|-
|-
! !! Local Processing !! Packet Mirroring
! Scenario !! Compatibility !! Notes
|-
|-
| '''<code>packetbuffer_sender</code>''' || <code>no</code> (default) || <code>yes</code>
| '''GUI ≥ Sniffer''' || ✅ Compatible || Recommended
|-
| '''Packet analysis''' || On remote sensor || On central server
|-
| '''PCAP storage''' || On remote sensor || On central server
|-
|-
| '''WAN bandwidth''' || Low (CDRs only) || High (full packets)
| '''GUI < Sniffer''' || ⚠️ Risk || Sensor may write to non-existent columns
|-
| '''Remote CPU load''' || Higher || Minimal
|-
| '''Use case''' || Standard multi-site || Low-resource remotes
|}
|}


=== PCAP Access in Local Processing Mode ===
'''Best practice:''' Upgrade GUI first (applies schema changes), then upgrade sensors.


When using Local Processing, PCAPs are stored on remote sensors. The GUI retrieves them via the central server, which proxies requests to each sensor's management port (TCP/5029).
For mixed versions temporarily, add to central server:
 
<syntaxhighlight lang="ini">
'''Firewall requirements:'''
server_cp_store_simple_connect_response = yes  # Sniffer 2024.11.0+
* Central server must reach remote sensors on TCP/5029
</syntaxhighlight>
* Remote sensors must reach central server on TCP/60024


== Dashboard Statistics ==
= Troubleshooting =


Dashboard widgets (SIP/RTP/REGISTER counts) depend on where packet processing occurs:
== Quick Diagnosis ==


{| class="wikitable"
{| class="wikitable"
|-
|-
! Configuration !! Where statistics appear
! Symptom !! First Check !! Likely Cause
|-
| Sensor not connecting || <code>journalctl -u voipmonitor -f</code> on sensor || Check <code>server_destination</code>, password, firewall
|-
| Traffic rate <code>[0.0Mb/s]</code> || tcpdump on sensor interface || Network/SPAN issue, not communication
|-
| High memory on central server || Check if <code>sipport</code> includes 60024 || Exclude server port from sipport
|-
| Missing calls || Compare <code>sipport</code> on probe vs central || Must match on both sides
|-
| "Bad password" error || GUI → Settings → Sensors || Delete stale sensor record, restart sensor
|-
| "Connection refused (111)" after migration || Check <code>server_destination</code> in config || Points to old server IP
|-
|-
| '''<code>packetbuffer_sender = yes</code>''' (Packet Mirroring) || Central server only
| RTP streams end prematurely || Check <code>natalias</code> location || Configure only on central server
|-
|-
| '''<code>packetbuffer_sender = no</code>''' (Local Processing) || Both sensor and central server
| Time sync errors || <code>timedatectl status</code> || Fix NTP or increase tolerance
|}
|}


'''Note:''' If you are using Packet Mirroring mode (<code>packetbuffer_sender=yes</code>) and see empty dashboard widgets for the forwarding sensor, this is expected behavior. The sender sensor only captures and forwards raw packets - it does not create database records or statistics. The central server performs all processing.
== Connection Testing ==


=== Enabling Local Statistics on Forwarding Sensors ===
<syntaxhighlight lang="bash">
# Test connectivity from sensor to server
nc -zv <server_ip> 60024


If you need local statistics on a sensor that was previously configured to forward packets:
# Verify server is listening
ss -tulpn | grep voipmonitor


<syntaxhighlight lang="ini">
# Check sensor logs
# On the forwarding sensor
journalctl -u voipmonitor -n 100 | grep -i "connect"
packetbuffer_sender = no
</syntaxhighlight>
</syntaxhighlight>


This disables packet forwarding and enables full local processing. Note that this increases CPU and RAM usage on the sensor since it must perform full SIP/RTP analysis.
== Time Synchronization Errors ==


== Controlling Packet Storage in Packet Mirroring Mode ==
If seeing "different time between server and client" errors:


When using Packet Mirroring (<code>packetbuffer_sender=yes</code>), the central server processes raw packets received from sensors. The <code>save*</code> options on the '''central server''' control which packets are saved to disk.
'''Immediate workaround:''' Increase tolerance on both sides:
<syntaxhighlight lang="ini">
client_server_connect_maximum_time_diff_s = 30
receive_packetbuffer_maximum_time_diff_s = 30
</syntaxhighlight>


<syntaxhighlight lang="ini">
'''Root cause fix:''' Ensure NTP is working:
# Central Server Configuration (receiving raw packets from sensors)
<syntaxhighlight lang="bash">
server_bind            = 0.0.0.0
timedatectl status          # Check sync status
server_bind_port        = 60024
chronyc tracking            # Check offset (Chrony)
server_password        = your_strong_password
ntpq -p                      # Check offset (NTP)
</syntaxhighlight>
 
== Network Throughput Testing ==


# Database Configuration
If experiencing "packetbuffer: MEMORY IS FULL" errors, test network with iperf3:
mysqlhost              = localhost
mysqldb                = voipmonitor
mysqluser              = voipmonitor
mysqlpassword          = db_password


# Sniffer options needed when receiving raw packets:
<syntaxhighlight lang="bash">
sipport                = 5060
# On central server
iperf3 -s


# CONTROL PACKET STORAGE HERE:
# On probe
# These settings on the central server determine what gets saved:
iperf3 -c <server_ip>
savertp                = yes          # Save RTP packets
savesip                = yes          # Save SIP packets
saveaudio              = wav          # Export audio recordings (optional)
</syntaxhighlight>
</syntaxhighlight>


{| class="wikitable" style="background:#e8f4f8; border:1px solid #4A90E2;"
{| class="wikitable"
|-
! Result !! Interpretation !! Action
|-
|-
! colspan="2" style="background:#4A90E2; color: white;" | Important: Central Server Controls Storage
| Expected bandwidth (>900 Mbps on 1Gb) || Network OK || Check local CPU/RAM
|-
|-
| style="vertical-align: top;" | '''Key Point:'''
| Low throughput || Network bottleneck || Check switches, cabling, consider Local Processing mode
| When sensors send raw packets to a central server, the storage is controlled by the <code>savertp</code>, <code>savesip</code>, and <code>saveaudio</code> options configured on the '''central server''', not on the individual sensors. The sensors are only forwarding raw packets - they do not make decisions about what to save unless you are using Local Processing mode.
|}
|}


This centralized control allows you to:
== Debugging SIP Traffic ==
* Enable/disable packet types (RTP, SIP, audio) from one location
 
* Adjust storage settings without touching each sensor
<code>sngrep</code> does not work on the central server because traffic is encapsulated in the TCP tunnel.
* Apply capture rules from the central server to filter traffic


== Data Storage Summary ==
'''Options:'''
* '''Live Sniffer:''' Use GUI → Live Sniffer to view SIP from remote sensors
* '''sngrep on sensor:''' Run <code>sngrep -i eth0</code> directly on the remote sensor


* '''CDRs''': Always stored in MySQL on central server
== Stale Sensor Records ==
* '''PCAPs''':
** Local Processing → stored on each remote sensor
** Packet Mirroring → stored on central server


== Handling Same Call-ID from Multiple Sensors ==
If a new sensor fails with "bad password" despite correct credentials:


When a call passes through multiple sensors that see the same SIP Call-ID, VoIPmonitor automatically merges the SIP packets into a single CDR on the central server. This is expected behavior when using Packet Mirroring mode.
# Delete the sensor record from '''GUI → Settings → Sensors'''
# Restart voipmonitor on the sensor: <code>systemctl restart voipmonitor</code>
# The sensor will re-register automatically


{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
= Legacy: Mirror Mode =
|-
! colspan="2" style="background:#ffc107;" | Call-ID Merging Behavior
|-
| style="vertical-align: top;" | '''What happens:'''
| If Sensor A and Sensor B both forward packets for a call with the same Call-ID to the central server, VoIPmonitor creates a single CDR containing SIP packets from both sensors. The RTP packets are captured from whichever sensor processed the media.
|-
| style="vertical-align: top;" | '''Why:'''
| VoIPmonitor uses the SIP Call-ID as the primary unique identifier. When multiple sensors forward packets with the same Call-ID to a central server, they are automatically treated as one call.
|-
| style="vertical-align: top;" | '''Is it a problem?'''
| Usually not. For most deployments, combining records from multiple sensors for the same call (different call legs passing through different points in the network) is the desired behavior.
|}


=== Preventing Duplicate CDRs in Local Processing Mode ===
The older <code>mirror_destination</code>/<code>mirror_bind</code> options still work but Client-Server mode is preferred (encryption, simpler management).


When using '''Local Processing mode''' (<code>packetbuffer_sender=no</code>), each remote probe processes its own packets and writes CDRs directly to a central database. If multiple probes capture the same call (e.g., redundant taps or overlapping SPAN ports), this creates '''duplicate CDR entries''' in the database.
To migrate from mirror mode:
# Stop sensors, comment out <code>mirror_*</code> parameters
# Configure <code>server_bind</code> on central, <code>server_destination</code> on sensors
# Restart all services


To prevent duplicates in this scenario, use the <code>cdr_check_exists_callid</code> option on '''all probes''':
For mirror mode <code>id_sensor</code> attribution, use:
<syntaxhighlight lang="ini">
# On central receiver
mirror_bind_sensor_id_by_sender = yes
</syntaxhighlight>


{| class="wikitable" style="background:#f8f9fa; border:1px solid #dee2e6;"
= See Also =
|-
! rowspan="2" | Setting
! colspan="2" | Result
|-
|<code>cdr_check_exists_callid = no</code> (default)
|Each probe creates its own CDR row. Multiple probes capturing the same call result in duplicate entries with the same Call-ID but different id_sensor values.
|-
|<code>cdr_check_exists_callid = yes</code>
|Probes check for an existing CDR with the same Call-ID before inserting. If found, they update the existing row instead of creating a new one. The final CDR will be associated with the id_sensor of the probe that last processed the call.
|}


'''Prerequisites:'''
* [[Sniffing_modes|Deployment & Topology Guide]] - Traffic forwarding methods
* MySQL user must have <code>UPDATE</code> privileges on the <code>cdr</code> table
* [[Sniffer_configuration|Sniffer Configuration]] - All parameters reference
* All probes must be configured with this setting
* [[Merging_or_correlating_multiple_call_legs|Call Correlation]] - Multi-leg call handling
* [[FAQ#One_GUI_for_multiple_sniffers|FAQ: One GUI for Multiple Sniffers]]


<syntaxhighlight lang="ini">
== Filtering Options in Packet Mirroring Mode ==
# Add to voipmonitor.conf on each probe (Local Processing mode only)
[general]
cdr_check_exists_callid = yes
</syntaxhighlight>


'''Note:''' This setting is only useful in Local Processing mode. In Packet Mirroring mode (<code>packetbuffer_sender=yes</code>), the central server automatically merges packets with the same Call-ID, so this option is not needed.
{{Note|1='''Important distinction:''' In Packet Mirroring mode (<code>packetbuffer_sender=yes</code>):


=== Keeping Records Separate Per Sensor ===
* '''Capture rules (GUI-based):''' Applied ONLY on the central server
* '''BPF filters / IP filters:''' CAN be applied on the remote sensor to reduce bandwidth


If you need to keep records completely separate when multiple sensors see the same Call-ID (e.g., each sensor should create its own independent CDR even for calls with overlapping Call-IDs), you must run '''multiple receiver instances on the central server'''.
Use the following options on the '''remote sensor''' to filter traffic BEFORE sending to the central server:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
# Receiver Instance 1 (for Sensor A)
# On REMOTE SENSOR (client)
[receiver_sensor_a]
 
server_bind            = 0.0.0.0
# Option 1: BPF filter (tcpdump syntax) - most flexible
server_bind_port        = 60024
filter = not net 192.168.0.0/16 and not net 10.0.0.0/8
mysqlhost              = localhost
mysqldb                = voipmonitor
mysqluser              = voipmonitor
mysqlpassword          = <password>
mysqltableprefix        = sensor_a_  # Separate CDR tables
id_sensor              = 2
# ... other options


# Receiver Instance 2 (for Sensor B)
# Option 2: IP allow-list filter - CPU-efficient, no negation support
[receiver_sensor_b]
interface_ip_filter = 192.168.1.0/24
server_bind            = 0.0.0.0
interface_ip_filter = 10.0.0.0/8
server_bind_port        = 60025  # Different port
mysqlhost              = localhost
mysqldb                = voipmonitor
mysqluser              = voipmonitor
mysqlpassword          = <password>
mysqltableprefix        = sensor_b_  # Separate CDR tables
id_sensor              = 3
# ... other options
</syntaxhighlight>
</syntaxhighlight>


Each receiver instance runs as a separate process, listens on a different port, and can write to separate database tables (using <code>mysqltableprefix</code>). Configure each sensor to connect to its dedicated receiver port.
<b>Benefits of filtering on remote sensor:</b>
* Reduces WAN bandwidth usage between sensor and central server
* Reduces processing load on central server
* Use <code>filter</code> for complex conditions (tcpdump/BPF syntax)
* Use <code>interface_ip_filter</code> for simple IP allow-lists (more efficient)


For more details on correlating multiple call legs from the same call, see [[Merging_or_correlating_multiple_call_legs]].
<b>Filtering approaches:</b>
* For <b>SIP header-based filtering</b>: Apply capture rules on the '''central server''' only
* For <b>IP/subnet filtering</b>: Use <code>filter</code> or <code>interface_ip_filter</code> on '''remote sensor'''}}


== GUI Visibility ==
== Supported Configuration Options in Packet Mirroring Mode ==


Remote sensors appear automatically when connected. To customize names or configure additional settings:
In Packet Mirroring mode (<code>packetbuffer_sender = yes</code>), the remote sensor forwards raw packets without processing them. This means many configuration options that manipulate packet behavior are '''unsupported''' on the remote sensor.
# Go to '''GUI → Settings → Sensors'''
# Sensors are identified by their <code>id_sensor</code> value


== Troubleshooting Distributed Deployments ==
== Supported Options on Remote Sensor (packetbuffer_sender) ==


=== Probe Not Detecting All Calls on Expected Ports ===
The following options work correctly on the remote sensor in packet mirroring mode:


If a remote sensor (probe) configured for packet mirroring is not detecting all calls on expected ports, check configuration on '''both''' the probe and the central analysis host.
{| class="wikitable"
 
! Parameter !! Description
{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
| <code>id_sensor</code> || Unique sensor identifier
|-
| <code>server_destination</code> || Central server address
|-
| <code>server_destination_port</code> || Central server port (default 60024)
|-
| <code>server_password</code> || Authentication password
|-
| <code>server_destination_timeout</code> || Connection timeout settings
|-
| <code>server_destination_reconnect</code> || Auto-reconnect behavior
|-
| <code>filter</code> || BPF filter to limit capture (use this to capture only SIP)
|-
| <code>interface_ip_filter</code> || IP-based packet filtering
|-
| <code>interface</code> || Capture interface
|-
| <code>sipport</code> || SIP ports to monitor
|-
| <code>promisc</code> || Promiscuous mode
|-
| <code>rrd</code> || RRD statistics
|-
| <code>spooldir</code> || Temporary packet buffer directory
|-
| <code>ringbuffer</code> || Ring buffer size for packet mirroring
|-
| <code>max_buffer_mem</code> || Maximum buffer memory
|-
|-
! colspan="2" style="background:#ffc107;" | Critical: sipport Must Match in Distributed Deployments
| <code>packetbuffer_enable</code> || Enable packet buffering
|-
|-
| style="vertical-align: top;" | '''The Issue:'''
| <code>packetbuffer_compress</code> || Enable compression for forwarded packets
| In distributed/probe setups using Packet Mirroring (<code>packetbuffer_sender=yes</code>), calls will be missing if the <code>sipport</code> configuration is not aligned between the probe and central server. Common symptom: Probe sees traffic via <code>tcpdump</code> but central server records incomplete CDRs.
|-
|-
| style="vertical-align: top;" | '''Configuration Requirement:'''
| <code>packetbuffer_compress_ratio</code> || Compression ratio
| The probe and central host must have consistent <code>sipport</code> values. If your network uses SIP on multiple ports (e.g., 5060, 5061, 5080, 6060), ALL ports must be listed on both systems.
|}
|}


The solution involves three steps:
== Unsupported Options on Remote Sensor ==


;1. Verify traffic reachability on the probe:
The following options '''do NOT work''' on the remote sensor in packet mirroring mode because the sensor does not parse packets:
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 5060
</pre>


;2. Check the probe's ''voipmonitor.conf'':
{| class="wikitable"
Ensure the <code>sipport</code> directive on the probe includes all necessary SIP ports used in your network.
! Parameter !! Reason
<syntaxhighlight lang="ini">
|-
# /etc/voipmonitor.conf on the PROBE
| <code>natalias</code> || NAT alias handling (configure on central server instead)
sipport = 5060,5061,5080,6060
|-
</syntaxhighlight>
| <code>rtp_check_both_sides_by_sdp</code> || RTP correlation requires packet parsing
 
|-
;3. Check the central analysis host's ''voipmonitor.conf'':
| <code>disable_process_sdp</code> || SDP processing happens on central server
'''This is the most common cause of missing calls in distributed setups.''' The central analysis host (specified by <code>server_bind</code> on the central server, or by <code>server_destination</code> configured on the probe) must also have the <code>sipport</code> directive configured with the same list of ports used by all probes.
<syntaxhighlight lang="ini">
# /etc/voipmonitor.conf on the CENTRAL HOST
sipport = 5060,5061,5080,6060
</syntaxhighlight>
 
;4. Restart both services:
Apply the configuration changes:
<syntaxhighlight lang="bash">
# On both probe and central host
systemctl restart voipmonitor
</syntaxhighlight>
 
{| class="wikitable" style="background:#e8f4f8; border:1px solid #4A90E2;"
|-
|-
! colspan="2" style="background:#4A90E2; color: white;" | Why Both Systems Must Match
| <code>save_sdp_ipport</code> || SDP extraction happens on central server
|-
|-
| style="vertical-align: top;" | '''Probe side:'''
| <code>rtpfromsdp_onlysip</code> || RTP mapping requires packet parsing
| 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>rtpip_find_endpoints</code> || Endpoint discovery requires packet parsing
| 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.
|}
|}


=== Quick Diagnosis Commands ===
{{Warning|1='''Critical: Storage options''' (<code>savesip</code>, <code>savertp</code>, <code>saveaudio</code>) '''must be configured on the CENTRAL SERVER''' in packet mirroring mode. The remote sensor only forwards packets and does not perform any storage operations.}}


On the probe:
== SIP-Only Capture Example ==
<syntaxhighlight lang="bash">
# Check which sipport values are configured
grep -E "^sipport" /etc/voipmonitor.conf


# Verify traffic is arriving on expected ports
To capture and forward only SIP packets (excluding RTP/RTCP) for security or compliance:
tcpdump -i eth0 -nn -c 10 port 5061
</syntaxhighlight>


On the central server:
<syntaxhighlight lang="ini">
<syntaxhighlight lang="bash">
# /etc/voipmonitor.conf - Remote Sensor
# Check which sipport values are configured
id_sensor              = 2
grep -E "^sipport" /etc/voipmonitor.conf
server_destination      = central.server.ip
server_destination_port = 60024
server_password        = your_strong_password
packetbuffer_sender    = yes
interface              = eth0
sipport                = 5060,5061


# Check syslog for analysis activity (should see processing packets)
# Filter to capture ONLY SIP packets (exclude RTP/RTCP)
tail -f /var/log/syslog | grep voipmonitor
filter = port 5060 or port 5061
</syntaxhighlight>
</syntaxhighlight>


If probes still miss calls after ensuring <code>sipport</code> matches on both sides, check the [[Sniffer_troubleshooting|full troubleshooting guide]] for other potential issues such as network connectivity, firewall rules, or interface misconfiguration.
{{Note|1=The <code>filter</code> parameter using BPF syntax (tcpdump-compatible) is the recommended way to filter packets at the source in packet mirroring mode. This reduces bandwidth by forwarding only SIP packets to the central server.}}
 


== Legacy: Mirror Mode ==


'''Note:''' The older <code>mirror_destination</code>/<code>mirror_bind</code> options still exist but the modern Client-Server approach with <code>packetbuffer_sender=yes</code> is preferred as it provides encryption and simpler management.


== Critical Requirement: SIP and RTP must be captured by the same sniffer instance ==


'''VoIPmonitor cannot reconstruct a complete call record if SIP signaling and RTP media are captured by different sniffer instances.'''


{| class="wikitable" style="background:#fff3cd; border:1px solid #ffc107;"
|-
! colspan="2" style="background:#ffc107;" | Important: Single sniffer requirement
|-
| style="vertical-align: top;" | '''What does not work:'''
| * Sniffer A in Availability Zone 1 captures SIP signaling
* Sniffer B in Availability Zone 2 captures RTP media
* Result: Incomplete call record, GUI cannot reconstruct the call
|-
| style="vertical-align: top;" | '''Why:'''
| Call correlation requires a '''single sniffer instance to process both SIP and RTP packets from the same call'''. The sniffer correlates SIP signaling (INVITE, BYE, etc.) with RTP media in real-time during packet processing. If packets are split across multiple sniffers, the correlation cannot occur.
|-
| style="vertical-align: top;" | '''Solution:'''
| Forward traffic so that '''one sniffer processes both SIP and RTP for each call'''. Options:
* Route both SIP and RTP through the same Availability Zone for capture
* Use Packet Mirroring mode to forward complete traffic (SIP+RTP) to a central server that processes everything
* Configure network routers/firewalls to forward the required stream to the correct zone
|}


Configuration parameters like <code>receiver_check_id_sensor</code> and <code>cdr_check_exists_callid</code> are for other scenarios (multipath routing, duplicate Call-ID handling) and '''do NOT enable split SIP/RTP correlation'''. Setting these parameters does not allow SIP from one sniffer to be merged with RTP from another sniffer.


== Limitations ==
= AI Summary for RAG =


* All sensors must use the same <code>server_password</code>
'''Summary:''' VoIPmonitor v20+ Client-Server architecture for distributed deployments using encrypted TCP (default port 60024, zstd compression). Two modes: '''Local Processing''' (<code>packetbuffer_sender=no</code>) analyzes locally and sends CDRs only (1Gb sufficient); '''Packet Mirroring''' (<code>packetbuffer_sender=yes</code>) forwards raw packets to central server. Critical requirements: (1) exclude server_bind_port from sipport on central server (prevents memory issues); (2) sipport must match on probe and central server; (3) single sniffer must process both SIP and RTP for same call; (4) natalias only on central server. Intermediate servers supported for hub-and-spoke topology. Use <code>manager_ip</code> to bind outgoing connections to specific IP on HA setups. Sensor health via management API port 5029: <code>echo 'sniffer_stat' | nc <ip> 5029</code>. Debug SIP using Live Sniffer in GUI or sngrep on remote sensor. Stale sensor records cause "bad password" errors - delete from GUI Settings → Sensors and restart. Time sync errors: fix NTP or increase <code>client_server_connect_maximum_time_diff_s</code>.
* A single sniffer cannot be both server and client simultaneously
* Each sensor requires a unique <code>id_sensor</code> (< 65536)
* Time synchronization (NTP) is critical for correlating calls across sensors
* Maximum allowed time difference between client and server: 2 seconds (configurable via <code>client_server_connect_maximum_time_diff_s</code>)


For a complete reference of all client-server parameters, see [[Sniffer_configuration#Distributed_Operation:_Client/Server_&_Mirroring|Sniffer Configuration: Distributed Operation]].
'''Keywords:''' distributed architecture, client-server, packetbuffer_sender, local processing, packet mirroring, server_destination, server_bind, sipport exclusion, AWS VPC Traffic Mirroring alternative, intermediate server, sensor health, sniffer_stat, Live Sniffer, natalias, version compatibility, time synchronization, NTP, stale sensor record, mirror mode migration, manager_ip, high availability


== AI Summary for RAG ==
'''Summary:''' VoIPmonitor v20+ uses Client-Server architecture for distributed deployments with encrypted TCP connections (default port 60024 with zstd compression, configurable via server_bind_port and server_destination_port). Two modes: Local Processing (<code>packetbuffer_sender=no</code>) analyzes locally and sends CDRs, Packet Mirroring (<code>packetbuffer_sender=yes</code>) forwards raw packets. Dashboard widgets for SIP/RTP/REGISTER counts: with Packet Mirroring, statistics appear only on central server (sender has empty widgets); with Local Processing, statistics appear on both sensor and central server. To enable local statistics on a forwarding sensor, set <code>packetbuffer_sender=no</code> (increases CPU/RAM usage). Supports failover with multiple server IPs. CDRs stored centrally; PCAPs on sensors (Local Processing) or centrally (Packet Mirroring). In Packet Mirroring mode, the <code>save*</code> options (savertp, savesip, saveaudio) configured on the CENTRAL SERVER control storage for packets received from sensors. When multiple sensors forward packets with the same Call-ID, VoIPmonitor automatically merges them into a single CDR. To keep records separate per sensor with same Call-ID, run multiple receiver instances on different ports with separate database tables. CRITICAL: A single sniffer instance MUST process both SIP signaling and RTP media for the same call. Splitting SIP and RTP across different sniffers creates incomplete call records that cannot be reconstructed. For custom port configuration: server_bind_port on central server MUST match server_destination_port on remote sensors. Common reasons for custom ports: firewall restrictions, multiple instances on same server, compliance requirements, avoiding port conflicts. TROUBLESHOOTING: In distributed/probe setups with Packet Mirroring, if a probe is not detecting all calls on expected ports, the <code>sipport</code> configuration MUST match on BOTH the probe AND the central analysis host. If the network uses multiple SIP ports (e.g., 5060, 5061, 5080), both systems must have all ports listed in their <code>sipport</code> directive. Common symptom: Probe sees traffic via <code>tcpdump</code> but central server records incomplete CDRs.
'''Keywords:''' distributed architecture, client-server, server_destination, server_bind, server_bind_port, server_destination_port, custom port, packetbuffer_sender, local processing, packet mirroring, remote sensors, failover, encrypted channel, zstd compression, dashboard widgets, statistics, empty dashboard, SIP RTP correlation, split sensors, single sniffer requirement, availability zone, savertp, savesip, saveaudio, centralized storage, packet storage control, call-id merging, multiple sensors same callid, separate records per sensor, receiver instances, mysqltableprefix, firewall, port configuration, connection troubleshooting, probe, central host, central server, sensor, sipport, missing calls, probe not detecting calls, tcpdump, configuration mismatch
'''Key Questions:'''
'''Key Questions:'''
* How do I connect multiple VoIPmonitor sensors to a central server?
* How do I connect multiple VoIPmonitor sensors to a central server?
* What is the difference between Local Processing and Packet Mirroring?
* What is the difference between Local Processing and Packet Mirroring mode?
* Where are CDRs and PCAP files stored in distributed mode?
* Why is VoIPmonitor using high memory on the central server?
* What is packetbuffer_sender and when should I use it?
* Why is a remote probe not detecting all calls on expected ports?
* How do I configure failover for remote sensors?
* How do I check VoIPmonitor sensor health status?
* Why are dashboard widgets (SIP/RTP/REGISTER counts) empty for a sensor configured to forward packets?
* Why does a new sensor fail with "bad password" error?
* How do I enable local statistics on a forwarding sensor?
* How do I migrate from mirror mode to client-server mode?
* Can VoIPmonitor reconstruct a call if SIP signaling is captured by one sniffer and RTP media by another?
* What causes time synchronization errors between client and server?
* Why does receiver_check_id_sensor not allow merging SIP from one sensor with RTP from another?
* Where should natalias be configured in distributed deployments?
* How do I control packet storage when sensors send raw packets to a central server?
* Can VoIPmonitor act as an intermediate server?
* What happens when multiple sensors see the same Call-ID?
* What is an alternative to AWS VPC Traffic Mirroring?
* How do I keep records separate when multiple sensors see the same Call-ID?
* How do I configure a custom port for client-server connections?
* What do I do if probes cannot connect to the VoIPmonitor server?
* Why is my remote sensor showing connection refused or timeout?
* Why is a voipmonitor sensor probe not detecting all calls on expected ports?
* Do I need to configure sipport on both the probe and central server in distributed setups?
* What happens if sipport configuration doesn't match between probe and central host?

Latest revision as of 20:48, 19 January 2026


This guide covers deploying multiple VoIPmonitor sensors in a distributed architecture using Client-Server mode (v20+).

For deployment options including on-host vs dedicated sensors and traffic forwarding methods (SPAN, GRE, TZSP, VXLAN), see VoIPmonitor Deployment & Topology Guide.

Overview

VoIPmonitor v20+ uses Client-Server architecture for distributed deployments. Remote sensors connect to a central server via encrypted TCP (default port 60024, zstd compression).

Mode packetbuffer_sender What is Sent Processing Location Use Case
Local Processing no (default) CDRs only Remote sensor Multi-site, low bandwidth
Packet Mirroring yes Raw packets Central server Centralized analysis, low-resource remotes

Use Cases

AWS VPC Traffic Mirroring Alternative: If experiencing packet loss with AWS VPC Traffic Mirroring (VXLAN overhead, MTU fragmentation), use client-server mode instead:

  • Install VoIPmonitor on each source EC2 instance
  • Send via encrypted TCP to central server
  • Eliminates VXLAN encapsulation and MTU issues

Configuration

Remote Sensor (Client)

id_sensor               = 2                    # Unique per sensor (1-65535)
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_strong_password

# Choose mode:
packetbuffer_sender     = no     # Local Processing: analyze locally, send CDRs
# packetbuffer_sender   = yes    # Packet Mirroring: send raw packets

interface               = eth0
sipport                 = 5060
# No MySQL credentials needed on remote sensors

💡 Tip: For HA setups with floating IPs, use manager_ip = 10.0.0.5 to bind outgoing connections to a static IP address.

Central Server

server_bind             = 0.0.0.0
server_bind_port        = 60024
server_password         = your_strong_password

mysqlhost               = localhost
mysqldb                 = voipmonitor
mysqluser               = voipmonitor
mysqlpassword           = db_password

# If receiving raw packets (packetbuffer_sender=yes on clients):
sipport                 = 5060
savertp                 = yes
savesip                 = yes

⚠️ Warning: Critical: Exclude server_bind_port from sipport on the central server. Including it causes continuously increasing memory usage. 

# WRONG - includes sensor communication port:
sipport = 1-65535

# CORRECT - excludes port 60024:
sipport = 1-60023,60025-65535

Key Configuration Rules

Rule Applies To Why
server_bind_port must match server_destination_port Both Connection fails if mismatched
sipport must match on probe and central server Packet Mirroring Missing ports = missing calls
natalias only on central server Packet Mirroring Prevents RTP correlation issues
Each sensor needs unique id_sensor All Required for identification

Local Processing vs Packet Mirroring

Local Processing Packet Mirroring
packetbuffer_sender no (default) yes
Processing location Remote sensor Central server
PCAP storage Remote sensor Central server
WAN bandwidth Low (CDRs only, 1Gb sufficient) High (full packets)
Remote CPU load Higher Minimal
Capture rules applied On sensor On central server only

PCAP Access in Local Processing Mode

PCAPs are stored on remote sensors. The GUI retrieves them through the central server, which proxies the request to the sensor over the existing TCP/60024 connection - the same persistent encrypted channel the sensor uses for sending CDRs. This connection is bidirectional; the central server does not open any separate connection back to the sensor.

Firewall requirements:

Direction Port Purpose
Remote sensors → Central server TCP/60024 Persistent encrypted channel (CDRs from sensor, PCAP requests from server - bidirectional)
GUI → Central server TCP/5029 Manager API (sensor status, active calls, configuration)
GUI → Central server TCP/60024 Server API (list connected sensors, proxy PCAP retrieval)

ℹ️ Note: The central server does not initiate connections to remote sensors. All server↔sensor communication happens over the single TCP/60024 connection that the sensor established.

💡 Tip: Packet Mirroring (packetbuffer_sender=yes) automatically deduplicates calls - the central server merges packets from all probes for the same Call-ID into a single unified CDR. This also ensures one logical call only consumes one license channel.

Advanced Topics

High Availability (Failover)

Remote sensors can specify multiple central servers: 

server_destination = 192.168.0.1, 192.168.0.2

If primary is unavailable, the sensor automatically connects to the next server.

Connection Compression

# On both client and server (default: zstd)
server_type_compress = zstd   # Options: zstd, gzip, lzo, none

Intermediate Server (Hub-and-Spoke)

An intermediate server can receive from multiple sensors and forward to a central server: 

# On INTERMEDIATE SERVER
id_sensor               = 100

# Receive from remote sensors
server_bind             = 0.0.0.0
server_bind_port        = 60024
server_password         = sensor_password

# Forward to central server
server_destination      = central.server.ip
server_destination_port = 60024

packetbuffer_sender     = no    # or yes, depending on desired mode

ℹ️ Note: This works because the intermediate server does NOT do local packet capture - it only relays. Original remote sensors must be manually added to GUI Settings for visibility.

Multiple Receivers for Packet Mirroring

⚠️ Warning: Multiple sensors with packetbuffer_sender=yes sending to a single receiver instance can cause call processing conflicts (calls appear in Active Calls but missing from CDRs).

Solution: Run separate receiver instances on different hosts, each dedicated to specific sensors: 

# Receiver Instance 1 (Host 1, for Sensor A)
server_bind_port        = 60024
id_sensor               = 1

# Receiver Instance 2 (Host 2, for Sensor B)
server_bind_port        = 60024
id_sensor               = 2

Alternative: Use Local Processing mode (packetbuffer_sender=no) which processes calls independently on each sensor.

Preventing Duplicate CDRs (Local Processing)

When multiple probes capture the same call in Local Processing mode: 

# On each probe
cdr_check_exists_callid = yes

This checks for existing CDRs before inserting. Requires MySQL UPDATE privileges.

Critical: SIP and RTP Must Be Captured Together

VoIPmonitor cannot correlate SIP and RTP from different sniffer instances. A single sniffer must process both SIP and RTP for each call. Parameters like cdr_check_exists_callid do NOT enable split SIP/RTP correlation.


Split SIP/RTP with Packet Mirroring Mode

ℹ️ Note: Exception for Packet Mirroring Mode:: The above limitation applies to Local Processing mode (packetbuffer_sender=no) where each sensor processes calls independently. In Packet Mirroring mode (packetbuffer_sender=yes), the central server receives raw packets from multiple remote sensors and processes them together. This allows scenarios where SIP and RTP are captured on separate nodes - configure both as packet senders and let the central server correlate them into single unified CDRs.

Example scenario: Separate SIP signaling node and RTP handling node: 

# SIP Signaling Node (packet sender)
id_sensor               = 1
packetbuffer_sender     = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_password

# RTP Handling Node (packet sender)
id_sensor               = 2
packetbuffer_sender     = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_password

The central server merges packets from both senders by Call-ID, creating unified CDRs with complete SIP and RTP data.


HEP Protocol in Client/Server Mode

VoIPmonitor supports receiving HEP-encapsulated traffic on sniffer clients and forwarding it to a central server. This enables distributed capture from HEP sources (Kamailio, OpenSIPS, rtpproxy, FreeSWITCH) in a client/server architecture.

Scenario: SIP proxy and RTP proxy at different locations sending HEP to remote sniffer clients: 

# Remote Sniffer Client A (receives HEP from Kamailio)
id_sensor               = 1
hep                     = yes
hep_bind_port           = 9060
packetbuffer_sender     = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_password

# Remote Sniffer Client B (receives HEP from rtpproxy)
id_sensor               = 2
hep                     = yes
hep_bind_port           = 9060
packetbuffer_sender     = yes
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_password

The central server receives packets from both clients and correlates them into unified CDRs using standard SIP Call-ID and IP:port from SDP.

ℹ️ Note: This also works for IPFIX (Oracle SBCs) and RibbonSBC protocols forwarded via client/server mode.

Alternative: Direct HEP to single sniffer

If both HEP sources can reach the same sniffer directly, no client/server setup is needed: 

# Single sniffer receiving HEP from multiple sources
hep                     = yes
hep_bind_port           = 9060
interface               = eth0   # Can also sniff locally if needed

Both Kamailio (SIP) and rtpproxy (RTP) send HEP to this sniffer on port 9060. The sniffer correlates them automatically based on Call-ID and SDP IP:port.

Sensor Health Monitoring

Management API

Query sensor status via TCP port 5029: 

echo 'sniffer_stat' | nc <sensor_ip> 5029

Returns JSON with status, version, active calls, packets per second, etc.

Multi-Sensor Health Check Script

#!/bin/bash
SENSORS=("192.168.1.10:5029" "192.168.1.11:5029")
for SENSOR in "${SENSORS[@]}"; do
    IP=$(echo $SENSOR | cut -d: -f1)
    PORT=$(echo $SENSOR | cut -d: -f2)
    STATUS=$(echo 'sniffer_stat' | nc -w 2 $IP $PORT 2>/dev/null | grep -o '"status":"[^"]*"' | cut -d'"' -f4)
    echo "$IP: ${STATUS:-FAILED}"
done

Version Compatibility

Scenario Compatibility Notes
GUI ≥ Sniffer ✅ Compatible Recommended
GUI < Sniffer ⚠️ Risk Sensor may write to non-existent columns

Best practice: Upgrade GUI first (applies schema changes), then upgrade sensors.

For mixed versions temporarily, add to central server: 

server_cp_store_simple_connect_response = yes   # Sniffer 2024.11.0+

Troubleshooting

Quick Diagnosis

Symptom First Check Likely Cause
Sensor not connecting journalctl -u voipmonitor -f on sensor Check server_destination, password, firewall
Traffic rate [0.0Mb/s] tcpdump on sensor interface Network/SPAN issue, not communication
High memory on central server Check if sipport includes 60024 Exclude server port from sipport
Missing calls Compare sipport on probe vs central Must match on both sides
"Bad password" error GUI → Settings → Sensors Delete stale sensor record, restart sensor
"Connection refused (111)" after migration Check server_destination in config Points to old server IP
RTP streams end prematurely Check natalias location Configure only on central server
Time sync errors timedatectl status Fix NTP or increase tolerance

Connection Testing

# Test connectivity from sensor to server
nc -zv <server_ip> 60024

# Verify server is listening
ss -tulpn | grep voipmonitor

# Check sensor logs
journalctl -u voipmonitor -n 100 | grep -i "connect"

Time Synchronization Errors

If seeing "different time between server and client" errors:

Immediate workaround: Increase tolerance on both sides: 

client_server_connect_maximum_time_diff_s = 30
receive_packetbuffer_maximum_time_diff_s = 30

Root cause fix: Ensure NTP is working: 

timedatectl status           # Check sync status
chronyc tracking             # Check offset (Chrony)
ntpq -p                      # Check offset (NTP)

Network Throughput Testing

If experiencing "packetbuffer: MEMORY IS FULL" errors, test network with iperf3: 

# On central server
iperf3 -s

# On probe
iperf3 -c <server_ip>
Result Interpretation Action
Expected bandwidth (>900 Mbps on 1Gb) Network OK Check local CPU/RAM
Low throughput Network bottleneck Check switches, cabling, consider Local Processing mode

Debugging SIP Traffic

sngrep does not work on the central server because traffic is encapsulated in the TCP tunnel.

Options:

  • Live Sniffer: Use GUI → Live Sniffer to view SIP from remote sensors
  • sngrep on sensor: Run sngrep -i eth0 directly on the remote sensor

Stale Sensor Records

If a new sensor fails with "bad password" despite correct credentials:

  1. Delete the sensor record from GUI → Settings → Sensors
  2. Restart voipmonitor on the sensor: systemctl restart voipmonitor
  3. The sensor will re-register automatically

Legacy: Mirror Mode

The older mirror_destination/mirror_bind options still work but Client-Server mode is preferred (encryption, simpler management).

To migrate from mirror mode:

  1. Stop sensors, comment out mirror_* parameters
  2. Configure server_bind on central, server_destination on sensors
  3. Restart all services

For mirror mode id_sensor attribution, use: 

# On central receiver
mirror_bind_sensor_id_by_sender = yes

See Also

Filtering Options in Packet Mirroring Mode

ℹ️ Note: Important distinction: In Packet Mirroring mode (packetbuffer_sender=yes):

  • Capture rules (GUI-based): Applied ONLY on the central server
  • BPF filters / IP filters: CAN be applied on the remote sensor to reduce bandwidth

Use the following options on the remote sensor to filter traffic BEFORE sending to the central server: 

# On REMOTE SENSOR (client)

# Option 1: BPF filter (tcpdump syntax) - most flexible
filter = not net 192.168.0.0/16 and not net 10.0.0.0/8

# Option 2: IP allow-list filter - CPU-efficient, no negation support
interface_ip_filter = 192.168.1.0/24
interface_ip_filter = 10.0.0.0/8

Benefits of filtering on remote sensor:

  • Reduces WAN bandwidth usage between sensor and central server
  • Reduces processing load on central server
  • Use filter for complex conditions (tcpdump/BPF syntax)
  • Use interface_ip_filter for simple IP allow-lists (more efficient)

Filtering approaches:

  • For SIP header-based filtering: Apply capture rules on the central server only
  • For IP/subnet filtering: Use filter or interface_ip_filter on remote sensor

Supported Configuration Options in Packet Mirroring Mode

In Packet Mirroring mode (packetbuffer_sender = yes), the remote sensor forwards raw packets without processing them. This means many configuration options that manipulate packet behavior are unsupported on the remote sensor.

Supported Options on Remote Sensor (packetbuffer_sender)

The following options work correctly on the remote sensor in packet mirroring mode:

Parameter Description
id_sensor Unique sensor identifier
server_destination Central server address
server_destination_port Central server port (default 60024)
server_password Authentication password
server_destination_timeout Connection timeout settings
server_destination_reconnect Auto-reconnect behavior
filter BPF filter to limit capture (use this to capture only SIP)
interface_ip_filter IP-based packet filtering
interface Capture interface
sipport SIP ports to monitor
promisc Promiscuous mode
rrd RRD statistics
spooldir Temporary packet buffer directory
ringbuffer Ring buffer size for packet mirroring
max_buffer_mem Maximum buffer memory
packetbuffer_enable Enable packet buffering
packetbuffer_compress Enable compression for forwarded packets
packetbuffer_compress_ratio Compression ratio

Unsupported Options on Remote Sensor

The following options do NOT work on the remote sensor in packet mirroring mode because the sensor does not parse packets:

Parameter Reason
natalias NAT alias handling (configure on central server instead)
rtp_check_both_sides_by_sdp RTP correlation requires packet parsing
disable_process_sdp SDP processing happens on central server
save_sdp_ipport SDP extraction happens on central server
rtpfromsdp_onlysip RTP mapping requires packet parsing
rtpip_find_endpoints Endpoint discovery requires packet parsing

⚠️ Warning: Critical: Storage options (savesip, savertp, saveaudio) must be configured on the CENTRAL SERVER in packet mirroring mode. The remote sensor only forwards packets and does not perform any storage operations.

SIP-Only Capture Example

To capture and forward only SIP packets (excluding RTP/RTCP) for security or compliance: 

# /etc/voipmonitor.conf - Remote Sensor
id_sensor               = 2
server_destination      = central.server.ip
server_destination_port = 60024
server_password         = your_strong_password
packetbuffer_sender     = yes
interface               = eth0
sipport                 = 5060,5061

# Filter to capture ONLY SIP packets (exclude RTP/RTCP)
filter = port 5060 or port 5061

ℹ️ Note: The filter parameter using BPF syntax (tcpdump-compatible) is the recommended way to filter packets at the source in packet mirroring mode. This reduces bandwidth by forwarding only SIP packets to the central server.





AI Summary for RAG

Summary: VoIPmonitor v20+ Client-Server architecture for distributed deployments using encrypted TCP (default port 60024, zstd compression). Two modes: Local Processing (packetbuffer_sender=no) analyzes locally and sends CDRs only (1Gb sufficient); Packet Mirroring (packetbuffer_sender=yes) forwards raw packets to central server. Critical requirements: (1) exclude server_bind_port from sipport on central server (prevents memory issues); (2) sipport must match on probe and central server; (3) single sniffer must process both SIP and RTP for same call; (4) natalias only on central server. Intermediate servers supported for hub-and-spoke topology. Use manager_ip to bind outgoing connections to specific IP on HA setups. Sensor health via management API port 5029: echo 'sniffer_stat' | nc <ip> 5029. Debug SIP using Live Sniffer in GUI or sngrep on remote sensor. Stale sensor records cause "bad password" errors - delete from GUI Settings → Sensors and restart. Time sync errors: fix NTP or increase client_server_connect_maximum_time_diff_s.

Keywords: distributed architecture, client-server, packetbuffer_sender, local processing, packet mirroring, server_destination, server_bind, sipport exclusion, AWS VPC Traffic Mirroring alternative, intermediate server, sensor health, sniffer_stat, Live Sniffer, natalias, version compatibility, time synchronization, NTP, stale sensor record, mirror mode migration, manager_ip, high availability

Key Questions:

  • How do I connect multiple VoIPmonitor sensors to a central server?
  • What is the difference between Local Processing and Packet Mirroring mode?
  • Why is VoIPmonitor using high memory on the central server?
  • Why is a remote probe not detecting all calls on expected ports?
  • How do I check VoIPmonitor sensor health status?
  • Why does a new sensor fail with "bad password" error?
  • How do I migrate from mirror mode to client-server mode?
  • What causes time synchronization errors between client and server?
  • Where should natalias be configured in distributed deployments?
  • Can VoIPmonitor act as an intermediate server?
  • What is an alternative to AWS VPC Traffic Mirroring?
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