Sniffer configuration

This document provides a comprehensive reference for all parameters in the `voipmonitor.conf` configuration file. It is designed to help administrators understand and tune the VoIPmonitor sensor for their specific environment.

The main configuration file is located at `/etc/voipmonitor.conf`. Additional configuration snippets can be placed in files within the `/etc/voipmonitor/conf.d/` directory (these should not contain the `[general]` section header).

Related documentation:

• Installation Guide - How to install the sniffer
• Distributed Architecture - Client/server deployment details
• Troubleshooting - Common issues and solutions
• Scaling Guide - Performance tuning for high traffic
• Data Cleaning - Retention and cleanup configuration

General & Core Settings

Time and Sensor Identification

id_sensor = 1

(Default: unset) A unique numeric identifier (1-65535) for this sensor. This is essential in multi-sensor deployments to distinguish which sensor captured a call. The value is stored in the `cdr.id_sensor` column.

utc = yes

(Default: no) When set to `yes`, all timestamps for CDRs and PCAP files are stored in UTC. This is highly recommended for deployments with sensors in different timezones to ensure consistency.

timezone = /usr/share/zoneinfo/UTC

(Default: system timezone) Overrides the system's default timezone by specifying a path to a valid zoneinfo file. Use this only if you need the sensor to operate in a timezone different from the server it's running on.

Deprecated and Removed Configuration Options

When upgrading the VoIPmonitor sensor to version 2025.09.1 or newer, some legacy configuration options are no longer supported and must be removed from /etc/voipmonitor.conf. Keeping these unsupported options can cause confusion and prevent the sensor from applying correct default behaviors.

⚠️ Warning: The options listed below are unsupported and ignored in sniffer version 2025.09.1 and later. Remove them from your configuration file.

VXLAN Options (Removed)

The following legacy VXLAN options were removed in favor of the modern udp_port_vxlan directive:

vxlan

Deprecated. Use udp_port_vxlan = 4789 instead.

vxlan_port

Deprecated. Use udp_port_vxlan = 4789 instead.

vxlan_skipcrc

Deprecated. This option is no longer supported.

Packet Buffer and UDP Reassembly Options (Removed)

packet_buffer_total_size

Deprecated. The packet buffer memory is now managed automatically via max_buffer_mem.

udp_reassembly

Deprecated. UDP reassembly is now controlled by udpfrag = yes.

udp_reassembly_max_size

Deprecated. The system automatically handles fragment sizes.

SIP Defragmentation and Processing Options (Removed)

sipdefrag

Deprecated. SIP defragmentation is now automatic.

sipdefrag_maxpacket

Deprecated. Defragmentation packet limits are handled internally.

defragment_max_size

Deprecated. Use max_sip_packets_in_call and max_invite_packets_in_call instead.

defragment_timeout

Deprecated. Packet processing timeouts are handled internally.

ignore_sip_parsing_errors

Deprecated. The sensor has improved error handling and this option is no longer needed.

sip_auto_clean

Deprecated. Automatic cleanup is now built-in.

max_sip_size

Deprecated. Use snaplen instead to control packet capture length.

sip_force_content_length

Deprecated. Content length handling is now automatic.

Validation and Interface Options (Removed)

sanity_checks

Deprecated. Enhanced validation is now built-in and cannot be disabled.

check_sip_header

Deprecated. SIP header validation is automatic.

interface_snaplen

Deprecated. Use snaplen instead (applies to all interfaces).

Modern Replacements

These options replace the deprecated ones above and should be used instead:

udp_port_vxlan = 4789

(Default: 4789) Port for VXLAN traffic in AWS and cloud environments. Use this instead of the legacy VXLAN options.

snaplen = 3200

(Default: 3200, 6000 if SSL/HTTP enabled) Packet capture length override. Replaces max_sip_size and interface_snaplen.

udpfrag = yes

(Default: yes) Enable IP fragment reassembly for UDP packets. Replaces udp_reassembly.

auto_enable_use_blocks = yes

(Default: no) Enables automatic memory block allocation for deduplication when sniffing from multiple sources or interfaces.

deduplicate = yes

(Default: no) Enables packet deduplication to identify and discard duplicate packets.

💡 Tip: After removing deprecated options, restart the sensor and check the logs for any "unknown option" warnings: journalctl -u voipmonitor -f

Process Management

watchdog = yes

(Default: no) If enabled, a watchdog process is created that automatically restarts the voipmonitor sensor if it crashes or is terminated unexpectedly.

watchdog_run_command = systemctl restart voipmonitor

(Default: unset) If specified, the watchdog will execute this command to restart the service instead of just re-running the binary. This is useful for proper service management with `systemd`.

Database Configuration

Connection Settings

mysqlhost = localhost

IP address or hostname of the MySQL/MariaDB server.

mysqlsocket = /var/run/mysqld/mysqld.sock

Path to the MySQL socket file for local connections (often faster than TCP).

mysqlport = 3306

TCP port of the database server.

mysqlusername = root

Username for the database connection.

mysqlpassword =

Password for the database connection.

mysqldb = voipmonitor

The name of the database to use. It will be created automatically if it doesn't exist.

mysql_connect_timeout = 60

(Default: 60) Timeout in seconds for establishing a connection to the database.

mysql_client_compress = no

(Default: no) Enables compression for the MySQL connection. Only use this if the database is on a remote, slow network link.

mysql_reconnect = yes

(Default: no) Enables automatic reconnection to the database if the connection is lost.

Database SSL/TLS

mysqlsslkey = /etc/ssl/client-key.pem

Path to the client's SSL private key file.

mysqlsslcert = /etc/ssl/client-cert.pem

Path to the client's SSL certificate file.

mysqlsslcacert = /etc/ssl/ca-cert.pem

Path to the Certificate Authority (CA) certificate file.

mysqlsslcapath = /etc/ssl/capath

Directory containing CA certificates.

mysqlsslciphers =

List of allowed SSL ciphers.

Performance & Schema

query_cache = yes

(Default: yes) This is a critical feature. When enabled, all SQL queries are first saved to a disk-based queue (qoq* files in the spool directory) before being sent to the database. This prevents data loss if the database is temporarily unavailable and prevents the sensor from running out of memory. When database connection is restored, the sensor writes the buffered CDRs from the queue files to the database. This process introduces a small delay but ensures no data loss during database downtime. If set to no, CDRs are held in sensor memory only during database outages, which can lead to OOM (Out Of Memory) situations and data loss if the database is offline for an extended period.

quick_save_cdr = no

(Default: no) Speeds up the visibility of calls in the GUI at the cost of higher system load. Options are `no` (10s delay, recommended), `yes` (3s delay), or `quick` (1s delay). Only change this if near-real-time CDR visibility is absolutely required.

cdr_partition = yes

(Default: yes) Enables partitioning for large tables (like `cdr`) by day. This is essential for performance and data management on any production system.

cdr_partition_by_hours = no

(Default: no) For extreme high-traffic environments (>= 15,000 CPS), this creates partitions per hour instead of per day to further improve performance.

disable_partition_operations = yes

(Default: no) Disables automatic partition creation. Useful when multiple sensors write to a single database and only one should manage partitions.

disable_dbupgradecheck = yes

(Default: no) If set to `yes`, the sniffer will not check for and apply database schema updates on startup.

mysqlloadconfig = yes

(Default: yes) When enabled, VoIPmonitor loads additional configuration parameters dynamically from the `sensor_config` database table (configured via the GUI). The GUI settings take priority over settings in `/etc/voipmonitor.conf`.

Important Behavior: If you modify the same parameter in both locations, the value from the database (GUI) is used and the file value is ignored. This is the default and recommended behavior for deployments using the web interface for configuration management. This setting also controls loading of the manager_key from the system table. If set to no, VoIPmonitor will NOT load the manager_key from the database, which will cause the sensor to fail to start with the error "failed read rsa key." For distributed manager/sensor deployments, ensure this option is enabled (or omitted for the default yes behavior) on both the manager and sensor to permit proper key exchange.

Troubleshooting Configuration File vs Database Conflicts

When mysqlloadconfig = yes (default), the sensor prioritizes configuration from the database over the configuration file. This can cause confusion if you edit settings in the file but do not also update them in the GUI, as your file changes will be silently ignored.

Symptoms of a Configuration Conflict:

• A parameter you changed in the configuration file has no effect
• Different values are shown in the GUI versus what you configured
• Settings revert after restarting the service

Diagnosing Conflicts via Syslog:

The sensor logs conflicting parameters to the system log at startup. To identify which settings are conflicting:

1. Restart the sensor service to trigger configuration logging:

systemctl restart voipmonitor

1. Check the system log for messages containing "Configuration values":

grep 'Configuration valu' /var/log/syslog

1. Filter to show only the parameter names and values:

cat /var/log/syslog | grep 'Configuration valu' -A 100 | grep ' / '

The log output shows parameters where the file and database values differ, for example:

Configuration values from configuration file and GUI (database) are different:
mysqlloadconfig = yes (active) - cleaning
/sensor_config/cleanspool vs /voipmonitor.conf/cleanspool = no
/sensor_config/maxpoolsize vs /voipmonitor.conf/maxpoolsize = 51200

In this example, the cleanspool and maxpoolsize settings are loaded from the database (GUI) rather than the configuration file.

Resolving Conflicts:

Choose one of these approaches based on your environment:

Option 1: Update via GUI (Recommended)

If you want to continue using the GUI for configuration management, ensure all parameter changes are made through the web interface:

1. Log in to the VoIPmonitor GUI
2. Navigate to Settings > Sensors
3. Click the wrench icon for the affected sensor
4. Update the desired parameter to match your intended configuration
5. Save the changes

The sensor will apply the new values immediately or upon the next reload.

Option 2: Disable MySQL Config Loading for File-Based Management

If you manage configuration exclusively via /etc/voipmonitor.conf or automation tools (Ansible, Puppet, etc.), disable database-driven configuration:

1. Edit the configuration file:

nano /etc/voipmonitor.conf

1. Add or modify this setting in the [general] section:

mysqlloadconfig = no

1. Restart the service:

systemctl restart voipmonitor

Warning: With this setting disabled, changes made via the GUI sensor settings page will be ignored.

Option 3: Remove Conflicting Database Entries

If you need to keep mysqlloadconfig = yes but want a specific parameter to use the file value instead of the database value:

1. Connect to the voipmonitor database:

mysql -u root -p voipmonitor

1. Check the current database value for the specific parameter:

SELECT * FROM sensor_config WHERE name = 'parameter_name';

1. Delete the conflicting entry to force the sensor to fall back to the file value:

DELETE FROM sensor_config WHERE name = 'parameter_name';

1. Verify deletion:

SELECT * FROM sensor_config WHERE name = 'parameter_name';

1. Restart the sensor:

systemctl restart voipmonitor

Best Practices:

• Decide on a single configuration source based on your management approach (GUI vs config file/automation)
• For GUI-based management, always use the web interface to modify settings
• For config file/automation management, set mysqlloadconfig = no to prevent conflicts
• Periodically review syslog for conflict warnings to catch discrepancies early
• After resolving conflicts, verify the active value with the syslog diagnostic command above

mysqlcompress_type = ...

(Default: auto-detected) You do not normally need to set this. The sniffer automatically chooses the best table compression method (LZ4 page compression) based on your MySQL/MariaDB version. Only change this for legacy systems.

mysql_enable_set_id = yes

(Default: no) In very high-traffic client/server deployments, this allows the central server to generate CDR IDs, which can improve batch insert performance.

cdr_force_primary_index_in_all_tables = no

(Default: no) Creates primary indexes on all tables. This is only required for specific database clustering technologies like MySQL/Galera Cluster and should not be enabled otherwise.

Important: This setting only affects table creation. When enabled, VoIPmonitor creates new tables with primary keys, but it does not modify existing tables or databases. If you have an existing database that was created without this setting enabled, you cannot simply enable it and expect existing tables to be retroactively fixed.

If you are deploying VoIPmonitor on a database cluster (such as Percona XtraDB Cluster in `ENFORCING` or `MASTER` mode) that requires all tables to have primary keys, follow this procedure:

1. Ensure cdr_force_primary_index_in_all_tables = yes is set in /etc/voipmonitor.conf on the sensor or aggregator node responsible for database creation.
2. Back up any important data from the existing voipmonitor database.
3. Drop the existing voipmonitor database.
4. Restart the VoIPmonitor service. It will automatically create a new database with the correct schema, including primary keys on all required tables.

⚠️ Warning: Dropping and recreating the database will delete all existing CDRs, messages, and other data. Ensure you have a backup before proceeding.

disable_cdr_fields_rtp = no

(Default: no) Disables all RTP-related statistics columns in the CDR table to save space.

sqlcallend = yes

(Default: yes) Enables storing `cdr.callend` (calldate + duration). Disable only if the column is missing.

SQL Queue Tuning

mysqlstore_concat_limit = 400

(Default: 400) Sets the global number of SQL statements to batch together before sending to the database.

mysqlstore_max_threads_cdr = 2

(Default: 2) The maximum number of parallel threads (and database connections) for writing CDRs. The sniffer will automatically scale up to this number if the queue grows.

Note: Separate `_concat_limit_*` and `_max_threads_*` options exist for `message`, `register`, `http`, etc.

server_sql_queue_limit = 1000000

(Default: 1000000) Limits the SQL queue size on the server side in client/server deployments. Set to 0 to disable.

server_sql_concat_limit = 5000

(Default: 1000) Number of queries to batch before confirming receipt in client/server mode.

Database Cleaning

cleandatabase = 0

(Default: 0, disabled) The master setting for database cleaning. Defines the retention period in days for CDRs and several other tables. Requires partitioning to be enabled.

cleandatabase_cdr = 0

(Default: 0, disabled) Specific retention period for `cdr` and `message` tables.

cleandatabase_rtp_stat = 2

(Default: 2) Retention period in days for detailed RTP statistics.

cleandatabase_register_failed = 0

(Default: 0) Retention for `register_failed` table.

cleandatabase_register_state = 0

(Default: 0) Retention for `register_state` table.

cleandatabase_sip_msg = 0

(Default: 0) Retention for `sip_msg` table (OPTIONS/SUBSCRIBE/NOTIFY).

cleandatabase_ss7 = 0

(Default: 0) Retention for `ss7` table.

cleandatabase_cdr_rtp_energylevels = 0

(Default: 0) Retention for energy levels table.

partition_operations_enable_fromto = 1-5

(Default: 1-5) Restricts partition-dropping operations to a specific time window (e.g., 1 AM to 5 AM) to avoid impacting performance during peak hours.

cleandatabase_size = 500000

(Default: unset) An alternative cleaning method that removes old data to stay below a total database size limit (in MB).

CDR Summary (Aggregation)

The CDR Summary feature pre-aggregates call data into intervals for significantly faster dashboard and reporting queries. See CDR_Summary for complete documentation including GUI behavior.

cdr_summary = yes

(Default: no) Enables the CDR summary feature. When enabled, the sniffer creates a cdr_summary table and continuously aggregates CDR data by sipcallerip, sipcalledip, payload, and last_sip_response.

cdr_summary_interval = 5

(Default: 5) The aggregation interval in minutes. Data is grouped into buckets of this size.

cleandatabase_cdr_summary = 0

(Default: 0, uses cleandatabase setting) Optional separate retention period in days specifically for the cdr_summary table. If not set, the main cleandatabase setting is used.

SQL Error Logging

sql_log_all_errors = no

(Default: no) Logs all SQL errors to syslog.

sql_errors_log_file = /path/to/log

(Default: unset) Redirects SQL error logging to a specific file.

sql_errors_skip = 1054,1136

(Default: unset) A comma-separated list of SQL error codes to ignore and not log.

Network Interface & Sniffing

This section configures how the sensor captures packets.

Interface Selection

interface = eth0

Specifies the network interface(s) to listen on. Use a comma-separated list for multiple interfaces (e.g., `eth0,eth1`). Using `any` will listen on all interfaces but will not enable promiscuous mode.

promisc = yes

(Default: yes) Puts the specified interface(s) into promiscuous mode to capture all traffic, not just traffic addressed to the server. Does not work with `interface = any`.

interfaces_optimize = yes

(Default: yes) Allows voipmonitor to automatically tune NIC settings like ring buffers and coalescing using `ethtool`.

eth_max_channels = 0

(Default: 0) Sets number of NIC interrupt queues. 0 means no change.

filter = udp or (vlan and udp)

(Default: unset) Applies a BPF filter (like in `tcpdump`) to the captured traffic. The `filter` option is processed by libpcap using Berkeley Packet Filter (BPF) syntax and supports tcpdump-style expressions including negation ('not'), logical operators ('and', 'or'), parentheses, and complex criteria matching IP addresses, ports, protocols, VLAN tags, and other packet fields. However, it can be CPU-intensive and complex to configure correctly. Warning: Using filters can accidentally exclude important traffic like VLAN-tagged or tunneled packets. Use with caution.

Example: Exclude specific subnets from being captured

# Exclude internal networks from capturing
filter = not net 192.168.0.0/16 and not net 10.0.0.0/8

Example: Capture only UDP SIP traffic

filter = udp port 5060

When modifying the `filter` setting, you must restart the sniffer service for changes to take effect: `systemctl restart voipmonitor`.

interface_ip_filter = 192.168.0.0/24

(Default: unset) A CPU-efficient method to filter traffic by IP address or subnet. This option matches packets whose source or destination IP falls within the specified networks. Multiple lines can be used to define multiple allowed networks. Unlike the main `filter` option, `interface_ip_filter` is an allow-list (whitelist) that implicitly discards traffic not matching any of the specified networks. It does not support negation or complex BPF syntax.

Example: Allow only internal traffic

# Only process packets from/to these networks
interface_ip_filter = 192.168.0.0/24
interface_ip_filter = 10.0.0.0/8

snaplen = 3200

(Default: 3200, 6000 if SSL/HTTP enabled) Packet capture length override. This parameter controls how many bytes of each packet are captured. If a SIP packet exceeds this limit, it is truncated and the sniffer may fail to parse the call correctly, resulting in missing CDRs.

Optimizing for Shared Server Deployments

When the VoIPmonitor sniffer runs on the same server as the PBX and RTP engine, resource contention can cause voice breakage and call lag. The sniffer competes for CPU cycles and network interrupts with the real-time media processing.

Symptoms:

• Audio breakage (jitter, packet loss)
• Call lag or delay
• Issues resolve when the sniffer is stopped

Solution 1: Specify Specific Interfaces Instead of using `interface = any`, specify a comma-separated list of the exact network interfaces that handle VoIP traffic:

# Instead of:
# interface = any

# Use specific interfaces:
interface = ens192,ens224

This creates a dedicated capture thread for each interface, improving performance on shared servers. Ensure the interfaces you specify are the ones carrying VoIP traffic.

Solution 2: Disable Automatic Interface Optimization If performance issues persist after specifying specific interfaces, disable automatic NIC optimization:

# Disable automatic tuning of NIC settings
interfaces_optimize = no

Note: This option requires the `ethtool` utility to be installed on the system.

Solution 3: Reduce Sniffer Load For immediate relief, configure the sniffer to reduce CPU consumption:

# Save only RTP headers (metadata only, no audio payload)
# This prevents audio reconstruction but keeps the RTP analysis tool functional
savertp = header

# Disable audio transcoding (very CPU intensive)
saveaudio = no

Long-term Recommendation: Move the VoIPmonitor sensor to a dedicated server connected via SPAN/Mirror port to eliminate resource contention entirely. See Sniffer_distributed_architecture for distributed deployment details.

Increase this value if you experience missing CDRs for calls with large SIP packets (e.g., INVITE requests with extensive SDP, many codec options, custom headers). Typical values are 65535 (maximum Ethernet frame size) or 20000.

To diagnose if packet truncation is the issue, use `tcpdump` with the `-s0` flag to capture full packets and verify packet sizes on your network.

High-Traffic Parallel Capture

For environments with very high packet rates (>2.2M pps), you can split traffic across multiple processing threads:

interface_libpcap_filter = eth0 : port 5060

(Default: unset) Allows splitting traffic from a single physical interface into multiple parallel processing threads within voipmonitor, each with its own BPF filter. This is an advanced technique to overcome per-core CPU limits.

Example for splitting traffic:

# Split SIP and non-SIP traffic into separate processing threads
interface_libpcap_filter = eth0 : port 5060
interface_libpcap_filter = eth0 : not port 5060

Multiple Sensor Instances on One Server

When running multiple VoIPmonitor sensor instances on the same physical server to monitor different traffic sources, special configuration is required to prevent resource contention and excessive CPU usage.

Each instance will compete for CPU cores, memory, and database connections. Improper configuration can lead to high CPU load, memory exhaustion, and system instability after VoIPmonitor upgrades that introduce improved multi-threading capabilities.

Important: Newer VoIPmonitor versions have enhanced threading defaults. Existing multi-instance setups may experience unexpectedly high CPU load after an upgrade if the instances are not properly configured for resource sharing.

Memory Allocation

max_buffer_mem = 1000

(Default: 2000) Set this parameter in each instance's configuration file to limit the total buffer memory per instance. This prevents all instances from consuming all available RAM and causing swap usage. Set this value proportionally based on the number of instances and available RAM. For example, with 16GB RAM and 4 instances, set `max_buffer_mem = 4000` per instance.

Database Thread Throttling

When running multiple instances on one server, each instance spawning multiple database threads can overwhelm the MySQL connections pool and cause excessive CPU usage. Limit database threads per instance:

mysqlstore_max_threads_cdr = 1

(Default

2) Set to 1 in multi-instance deployments to reduce thread overhead.

mysqlstore_max_threads_message = 1

(Default

2) Limits parallel threads for storing MESSAGE records.

mysqlstore_max_threads_register = 1

(Default

2) Limits parallel threads for storing REGISTER data.

mysqlstore_max_threads_http = 1

(Default

2) Limits parallel threads for HTTP-related data.

Note: Reducing these values may slow down database writes during traffic bursts, but is necessary to prevent CPU overload when multiple instances compete for database resources.

Multi-Instance Configuration Example

# Instance 1 Configuration (/etc/voipmonitor/instance1.conf)
[general]
id_sensor = 1
pidfile = /var/run/voipmonitor/instance1.pid
interface = eth0
max_buffer_mem = 1000
mysqlstore_max_threads_cdr = 1
mysqlstore_max_threads_message = 1
mysqlstore_max_threads_register = 1
mysqlstore_max_threads_http = 1

# Instance 2 Configuration (/etc/voipmonitor/instance2.conf)
[general]
id_sensor = 2
pidfile = /var/run/voipmonitor/instance2.pid
interface = eth1
max_buffer_mem = 1000
mysqlstore_max_threads_cdr = 1
mysqlstore_max_threads_message = 1
mysqlstore_max_threads_register = 1
mysqlstore_max_threads_http = 1

Note on threading_expanded

The modern `threading_expanded` parameter (enabled by default) automatically manages threads. In some multi-instance scenarios where you have limited CPU cores, you may need to disable this and use the legacy `threading_mod = 1` for single-threaded processing per instance. However, this is deprecated and should only be used as a last resort.

Troubleshooting High CPU After Upgrade

If a multi-instance deployment experiences high CPU load after a VoIPmonitor upgrade:

1. Review system baseline load before the upgrade to determine if the server was already near capacity
2. Apply the memory and thread throttling settings above to each instance
3. Monitor `top` or `htop` to verify CPU usage is distributed properly
4. If CPU load remains high after these changes, the root cause may be insufficient hardware capacity. Consider upgrading the server to provide more CPU cores or distributing instances across multiple physical servers.

See also: Client/Server mode for an alternative to multi-instance deployments on a single host.

Tunneling Protocol Support

VoIPmonitor can decode various tunneling protocols. To enable listening, uncomment and configure the relevant port.

udp_port_tzsp = 37008

(Default: 37008) Mikrotik TZSP protocol.

udp_port_l2tp = 1701

(Default: 1701) L2TP tunneling.

udp_port_vxlan = 4789

(Default: 4789) VXLAN, common in AWS and cloud environments.

udp_port_hperm = 7932

(Default: 7932) HP ERM protocol.

audiocodes = yes

(Default: no) Enables AudioCodes proprietary tunnel.

udp_port_audiocodes = 925

Port for AudioCodes mirroring.

audiocodes_rtp = yes

Enable AudioCodes RTP processing. Options: no, yes, only, only_for_audiocodes_sip.

ipfix = yes

(Default: no) Enables IPFIX, used by Oracle/ACME SBCs. See IPFIX Support section.

hep = yes

(Default: no) Enables Homer Encapsulation Protocol. See HEP Support section.

kamailio_port = 5888

(Default: unset) Enables mirroring from Kamailio's `siptrace` module.

ribbonsbc = yes

(Default: no) Enables Ribbon SBC mirroring. See Ribbon SBC Mirroring section.

icmp_process_data = no

(Default: no) Extract SIP data from ICMP type 3 messages.

Packet Deduplication

When traffic is received from multiple sources or mirrored from multiple points, the same packet may arrive more than once. The deduplication feature identifies and discards duplicate packets based on checksum comparison.

Typical configuration for deduplication:

# Enable packet deduplication. Uses checksum to identify
# and discard duplicate packets. This is CPU intensive.
deduplicate = yes

# Required for deduplication to work correctly when
# packets are received from multiple sources or interfaces.
auto_enable_use_blocks = yes

# Count only IP addresses from IP header in the checksum.
# This is useful when the same packet arrives from different
# network paths with different TTL or other IP header fields.
deduplicate_ipheader = ip_only

deduplicate = yes

(Default: no) Enables packet deduplication based on a checksum (MD5 or the faster experimental "murmur" algorithm). Useful if you are receiving the same traffic stream from multiple sources or interfaces. Note: This is CPU intensive.

use_block = yes

(Default: no) Manually enables use of memory blocks for packet processing. This option is recommended in scenarios where the sniffer experiences high traffic loads or processing bottlenecks, particularly when symptoms include: (1) SIP registrations incorrectly shown as failed in the GUI even though packet captures on the sensor show the traffic is present, or (2) Missing call legs in CDRs despite complete packet captures. Memory blocks help the sniffer manage packet processing more efficiently, preventing drops during analysis bursts. This option is automatically enabled by `auto_enable_use_blocks = yes`, but can be set manually if needed.

auto_enable_use_blocks = yes

(Default: no) Required in two scenarios: (1) For deduplication when sniffing from multiple sources or interfaces to identify and discard duplicate packets, and (2) For correct RTP association when SIP signaling and RTP media arrive on different interfaces, NICs, or VLANs, preventing RTP packets from being associated with the wrong call leg. Automatically enables use of memory blocks for deduplication and defragmentation processing.

deduplicate_ipheader = ip_only

(Default: yes, meaning full IP header) Controls how the IP header is used in the deduplication checksum:

• yes (default): Include the full IP header in the checksum
• ip_only: Count only the source and destination IP addresses from the IP header. Recommended when packets arrive from different network paths that may modify TTL or other IP header fields.
• no: Exclude the IP header entirely from the checksum

deduplicate_ipheader_ignore_ttl = yes

(Default: yes) Ignore the TTL (Time To Live) field in the IP header when comparing packets. This prevents false negatives when the same packet arrives via different network hops.

deduplicate_udpheader_ignore_checksum = yes

(Default: yes) Exclude the UDP header checksum when comparing packets. Useful because some network equipment may recalculate the UDP checksum, causing identical payload packets to have different checksums.

Scan PCAP Directory Mode

scanpcapdir = /dev/shm/voipmonitor

(Default: unset) A special mode where the sensor does not capture live traffic but instead processes PCAP files from a directory as they are created by another tool, like `tcpdump`.

scanpcapmethod = newfile

(Default: newfile) Method for detecting new files. Options: newfile, rename.

scanpcapdir_thread = 1

(Default: 1) Number of threads for processing PCAP files in directory mode. Increasing this value can improve performance when processing multiple files, but may cause resource contention. Set to 0 or comment out to avoid threading overhead and performance issues in single-threaded scenarios. If you experience slow CDR processing when reading PCAP files from a directory, try disabling or reducing this setting.

This mode is useful in scenarios where live packet capture (SPAN/TAP) is not possible, such as:

• Monitoring traffic from a host where VoIPmonitor cannot run (e.g., Windows machines)
• Capturing traffic from isolated network segments without remote sensors
• Processing captured files from multiple sources in batch

Use Case: Monitoring from Windows Without SPAN Port

When you need to monitor VoIP traffic from a Windows host but port mirroring is not available, you can use the `scanpcapdir` mode as an alternative:

Step 1: Capture PCAP files on the Windows host

# On Windows (using WSL, Cygwin, or a Linux machine that can see the traffic)
# Capture UDP traffic to a rolling pcap file (rotates every 5 minutes)
tcpdump -i eth0 udp -G 300 -w /path/to/capture/dump.pcap

# Or use the -C option to rotate by file size (e.g., 100MB)
tcpdump -i eth0 udp -C 100 -w /path/to/capture/dump.pcap

Step 2: Transfer PCAP files to the VoIPmonitor server

Use any file transfer method (SCP, SFTP, NFS, SMB share, rsync, etc.) to move the PCAP files to a directory accessible by the VoIPmonitor sensor.

# Example rsync command (run from Windows via WSL or SSH)
rsync -avz /path/to/capture/dump.pcap user@voipmonitor-server:/var/spool/voipmonitor/scanpcap/

# Or mount the Windows directory and have tcpdump write directly to it
# (ensure the mount is stable and handles file locking correctly)

Step 3: Configure VoIPmonitor to scan the directory

Edit /etc/voipmonitor.conf:

[general]
# Disable live capture (interface is not used in scanpcapdir mode)
# interface = eth0  <-- Leave this commented out

# Point to the directory containing the pcap files
scanpcapdir = /var/spool/voipmonitor/scanpcap

# Method: 'newfile' detects new files by modification time
# 'rename' requires files to be written to a temp location and then renamed
scanpcapmethod = newfile

Step 4: Restart VoIPmonitor

systemctl restart voipmonitor

VoIPmonitor will now automatically scan the specified directory and process any new PCAP files, extracting call data, CDRs, and saving recordings if enabled.

Important Notes:

• When using `scanpcapdir`, the interface setting is not used
• Ensure the sensor has read permissions for the pcap files and directory
• The sensor processes each file exactly once and does not re-process already handled files
• Large pcap files (gigabytes in size) may take significant time to process
• Consider using savertp = header if you only need call metadata and not full audio
• File rotation (using `-G` or `-C` in tcpdump) prevents single large files from blocking processing

SIP Send (Third-Party Forwarding)

sip_send = 192.168.0.2:1555

(Default: unset) Forwards a copy of all captured SIP packets to a specified third-party destination over TCP or UDP. This is not for mirroring between sensors.

sip_send_udp = yes

(Default: no) Use UDP instead of TCP for sip_send.

sip_send_before_packetbuffer = yes

(Default: no) Send packets immediately without buffering.

SIP Port & TCP Configuration

SIP Port Settings

sipport = 5060

(Default: 5060) Specifies the SIP ports that VoIPmonitor will listen to. Multiple ports can be specified: `sipport = 5060,5061,5062,5070-5080`.

cdr_sipport = yes

(Default: yes) Store SIP source and destination ports in the database.

cdr_rtpport = yes

(Default: yes) Store RTP destination port in the database.

cdr_rtpsrcport = no

(Default: no) Store RTP source port in the database.

CDR Country Configuration

cdr_country_code = yes

(Default: yes) Enables country code lookup and storage in CDR for caller and called number columns. When enabled, VoIPmonitor attempts to determine the country code from telephone numbers and stores the information in the `cdr.caller_country` and `cdr.called_country` columns. This allows the GUI to display country flags and filter CDRs by country. Set to `no` to disable country code detection and storage, which may be useful if you do not use country-based filtering or want to reduce processing overhead.

⚠️ Warning: Setting cdr_country_code = no disables country flags in the CDR view and prevents filtering by country, even if GeoIP and country prefix settings are configured. If country flags are not appearing in the GUI, check this setting and ensure it is set to yes (or commented out for default behavior).

TCP Reassembly

sip_tcp_reassembly_ext = yes

(Default: yes) Enable TCP reassembly for SIP over TCP.

sip_tcp_reassembly_stream_max_attempts = 50

(Default: 50) Maximum TCP reassembly attempts.

sip_tcp_reassembly_ext_link_timeout = 10

(Default: 10) TCP reassembly link timeout in seconds.

sip_tcp_reassembly_ext_quick_mod = no

(Default: no) Experimental quick mode for high traffic. Options: no, yes, ext, comb_ext.

UDP Fragmentation

udpfrag = yes

(Default: yes) Enable IP fragment reassembly for UDP packets. Large SIP messages (especially INVITE with SDP) may be fragmented at the IP layer when they exceed the MTU. When enabled, VoIPmonitor reassembles IP fragments before parsing SIP. Critical for missing SIP packets that contain large headers or SDP. Disable only for debugging purposes or when you are certain no fragmented traffic exists in your environment.

SIP Packet Limits

max_sip_packets_in_call = 2000

(Default: 2000) Maximum SIP packets per call.

max_invite_packets_in_call = 10000

(Default: 10000) Maximum SIP INVITE packets per call.

SIP TLS/SSL Decryption

To decrypt TLS-encrypted SIP traffic, you need to provide the private key. Note that Diffie-Hellman ciphers cannot be decrypted without session keys.

ssl = yes

(Default: no) Enable TLS/SSL decryption for SIP.

ssl_ipport = 10.0.0.1 : 5061 /path/to/your.key

(Default: unset) Specify IP:port and private key for decryption. Multiple keys can be separated by commas.

ssl_ipport = 10.0.0.0/24 : 5061 /path/to/your.key,/path/to/other.key

Example with subnet and multiple keys.

ssl_ipport_reverse_enable = yes

(Default: no) Enable reverse detection logic for ssl_ipport.

ssl_store_sessions_expiration_hours = 12

(Default: 12) SSL sessions expire after this many hours.

ssl_sessionkey_udp = yes

(Default: no) Enable parsing of session keys sent via UDP (keylogger support).

ssl_sessionkey_udp_port = 1234

UDP port for receiving session keys.

ssl_store_sessions = persistent

(Default: persistent) How to store SSL keys: 'persistent' (InnoDB) or 'memory'.

Choosing Between Storage Options

The ssl_store_sessions parameter controls where VoIPmonitor stores encryption keys for SSL/TLS sessions:

• persistent (Recommended): Stores keys in the ssl_sessions InnoDB table on disk. This provides virtually unlimited storage space and eliminates "table full" errors.

• memory (Legacy): Stores keys in the ssl_sessions_mem MEMORY table in RAM. This provides faster performance but has a hard size limit defined by MySQL's max_heap_table_size and the table's MAX_ROWS definition. When this table becomes full, VoIPmonitor cannot write new session keys, leading to decryption failures and data insertion errors.

Recovering from a Full ssl_sessions_mem Table

If you encounter errors because the ssl_sessions_mem table is full:

1. On the main database server, identify which sensor(s) are still writing to the memory table:

SELECT id_sensor, COUNT(*) FROM ssl_sessions_mem GROUP BY id_sensor;

2. Log into each identified sensor.

3. Edit /etc/voipmonitor.conf and ensure the setting is:

ssl_store_sessions = persistent

4. Restart the VoIPmonitor sniffer service on each sensor to apply the change. This will direct new SSL session keys to the persistent ssl_sessions InnoDB table:

systemctl restart voipmonitor

5. (Optional) Clear the existing data from the memory table on the database server:

TRUNCATE TABLE ssl_sessions_mem;

Note: After switching to persistent storage, ensure your regular database maintenance scripts or partitioning strategies account for the growth of the ssl_sessions table on disk to prevent the disk itself from filling up over time.

ssl_tls_12_sessionkey_mode = dssl

(Default: dssl) Decryption library: 'dssl' or 'wireshark'.

ssl_ignore_error_invalid_mac = yes

(Default: yes) Ignore SSL/TLS packets with invalid MAC.

SRTP Configuration

This section deals with Secure RTP (SRTP) decryption, including both RTP and RTCP streams. Supported encryption algorithms: AES_CM_128_HMAC_SHA1_32, AES_CM_128_HMAC_SHA1_80.

srtp_rtp = no

(Default: no) Decrypt and store RTP data in PCAPs. By default, only RTCP is decrypted.

srtp_rtcp = yes

(Default: yes) Decrypt RTCP streams.

srtp_rtp_dtmf = no

(Default: no) Decrypt only RTP DTMF packets.

srtp_rtp_dtls = yes

(Default: yes) Enable DTLS decryption. Requires keylogger or session keys.

ssl_dtls_queue = yes

(Default: no) Enable DTLS packet queue to prevent packet loss during decryption.

ssl_dtls_queue_expiration = 10

(Default: 10) DTLS queue expiration time in seconds.

srtp_rtp_local_instances = no

(Default: no) Create separate decryption instance per RTP stream.

ssl_dtls_queue_keep = no

(Default: no) Keep DTLS packets in queue after first successful use.

ssl_sessionkey_keep = no

(Default: no) Keep keylogger keys until expiration instead of discarding after first use.

ssl_dtls_handshake_safe = no

(Default: no) DTLS handling approach: no (queue), only (unified), yes (both, queue priority), ext (both, unified priority).

ssl_dtls_boost = no

(Default: no) A meta-parameter that enables a set of aggressive options for improving DTLS handshake and SRTP decryption success rates. When enabled, it sets:

• ssl_dtls_queue_expiration = 30
• ssl_sessionkey_keep = yes
• ssl_dtls_queue_keep = yes
• ssl_dtls_handshake_safe = ext
• ssl_dtls_rtp_local = yes

Caller/Called Identity Configuration

These options control how caller and called party information is extracted from SIP headers.

remoteparty_caller = calling

(Default: unset) Update caller number from Remote-Party-ID header. Use 'calling' or 'called' based on the party attribute.

remoteparty_called = called

(Default: unset) Update called number from Remote-Party-ID header.

passertedidentity = no

(Default: no) Use P-Asserted-Identity header for caller info.

ppreferredidentity = no

(Default: no) Use P-Preferred-Identity header for caller info.

remotepartypriority = no

(Default: no) Give Remote-Party-ID priority over P-Asserted-Identity and P-Preferred-Identity.

callernum_numberonly = yes

(Default: yes) Parse only the number part from identity headers.

destination_number_mode = 1

(Default: 1) Source for destination number: 1 = To header, 2 = INVITE URI.

sipoverlap = yes

(Default: yes) Update destination number from subsequent INVITEs (overlap dialing support per RFC 3578).

last_dest_number = no

(Default: no) Always take destination from latest INVITE regardless of source IP.

update_dstnum_onanswer = no

(Default: no) Update destination number when callee answers (useful for hunt groups).

Performance & Threading

Core Threading Model

t2_boost = high_traffic

(Default: unset) Optimizes the threading model for high-traffic environments (>=1500Mbit). This setting automatically adjusts thread allocation, which resolves CPU bottlenecks where a single defrag or reassembly thread runs at 100% while other threads are idle. Use this when you observe one thread at 100% CPU alongside "packetbuffer: MEMORY IS FULL" errors. Available values: `high_traffic` for very high bandwidth deployments, or `no` to disable.

threading_expanded = yes

(Default: yes) Enables the modern, multi-threaded processing engine. The sniffer automatically spawns and manages threads based on traffic load and CPU capacity. Set to `high_traffic` for environments exceeding 5 Gbit/s or very high concurrent call loads (8,000-10,000+ calls) where PACKETBUFFER saturation occurs.

preprocess_rtp_threads = 2

(Default: 2) The initial number of threads for RTP preprocessing. The system will auto-scale from here.

preprocess_rtp_threads_max = 5

(Default: unlimited) Maximum RTP preprocessing threads.

pre_process_packets_next_thread = 4

For high network throughput (>= 5Gbit), set to 4.

pre_process_packets_next_thread_max = 4

Hard limit is 4 even if value is higher.

destroy_calls_in_storing_cdr = yes

(Default: no) Offloads the process of freeing call memory to a separate thread. Useful in very high-traffic scenarios (> 50,000 concurrent calls).

rtpthreads_start = 20

(Default: rtpthreads value or half of CPU count) Starting number of RTP processing threads. For high concurrent call loads (8,000-10,000+ calls), set to approximately half of the total CPU count or a specific value like 20. This parameter directly influences RTP thread initialization and helps prevent PACKETBUFFER saturation under heavy load.

rtpthreads = 0

(Default: CPU count) Number of threads for RTP packet processing. 0 disables threading.

Thread Scheduling & Priority

sched_pol_auto = prio -20

(Default: `prio -20`) Automatically elevates the priority (lowers the `nice` value) of critical threads if the system comes under load.

sched_pol_auto_heap_limit = 1

(Default: 1) Heap growth percentage threshold for priority elevation.

sched_pol_auto_cpu_limit = 45

(Default: 45) CPU usage threshold for priority elevation.

Manual thread priority settings (alternative to auto):

sched_pol_interface = prio -20

sched_pol_pb = prio -20

sched_pol_sip = prio -20

sched_pol_rtp_prep = prio -20

sched_pol_rtp_read = prio -20

NUMA & Memory

numa_balancing_set = autodisable

(Default: autodisable) Manages the Linux kernel's NUMA balancing feature. The default setting will automatically disable NUMA balancing if it detects high overhead.

hugepages_max = 80000

(Default: 0, disabled) Enables the use of huge pages for memory allocation, which can improve performance on some systems by reducing TLB misses.

Buffer Configuration

ringbuffer = 50

(Default: 50) Ringbuffer size in MB. Recommended >= 500 for >100 Mbit traffic. Max 2000.

packetbuffer_enable = yes

(Default: yes) Enable packet buffer cache.

packetbuffer_compress = no

(Default: no) Enable packet buffer compression. In distributed client/server setups with multiple sensors, set to yes on client instances to reduce the data transfer rate to the central server and prevent packet buffer memory overflow errors.

packetbuffer_compress_ratio = 100

(Default: 100) Compression ratio for packet buffer compression (1-100). Higher values provide better compression at the cost of increased CPU usage. Use 100 for maximum compression to minimize network bandwidth in distributed setups.

max_buffer_mem = 2000

(Default: 2000) Maximum buffer memory in MB. Increase to 10000 or higher for high concurrent call loads (8,000-10,000+ calls) to prevent "PACKETBUFFER: memory is FULL" errors. In distributed setups with compression enabled, a reasonable value of 10000 helps prevent excessive queuing of old packets when network transfer rates cannot keep up with data generation. Ensure sufficient RAM is available.

memory_purge_interval = 30

(Default: 30) Memory purge interval in seconds.

memory_purge_if_release_gt = 500

(Default: 500) Memory purge threshold in MB.

Distributed Operation: Client/Server & Mirroring

VoIPmonitor supports distributed deployments where remote sensors send data to a central server. There are two operational modes controlled by the packetbuffer_sender parameter:

Key differences:

• Local Processing (packetbuffer_sender=no): Low network usage, PCAP files stored on remote sensor, higher CPU usage on sensor
• Packet Mirroring (packetbuffer_sender=yes): Higher network usage, all data centralized, minimal CPU usage on sensor

Modern Client/Server Model (Recommended)

server_bind = 0.0.0.0

The IP address the central sensor will listen on for connections from remote clients.

server_bind_port = 60024

(Default: 60024) Port for client connections.

server_destination = 10.0.0.1

The IP address of the central server a remote sensor should connect to. Multiple IPs for failover: `192.168.0.1, 192.168.0.2`.

server_destination_port = 60024

(Default: 60024) Port of the central server.

server_password =

A shared password to authenticate clients and servers.

packetbuffer_sender = no

(Default: no) The operational mode. `no` for local processing (low network usage), `yes` for packet mirroring (low remote CPU usage).

packetbuffer_file_path = /path/to/directory

Path to a local directory where CDR packets will be cached to disk when the connection to the central server is lost or temporarily unavailable. This provides a fallback queue for packet transmission during network outages. When the connection is restored, cached packets are transmitted. Note that the server may discard packets that are too old upon reconnection. (Default: not set - packets are buffered in memory only and lost if connection fails)

Important: packetbuffer_sender Controls Packet Transmission
Critical Behavior:	When packetbuffer_sender = yes, all packets are transmitted (forwarded to central server or sent via packet buffer), which includes RTP packets regardless of your savertp setting. This option always transmits full packet streams for processing.
If RTP is recorded despite savertp = no:	Check for packetbuffer_sender = yes in your configuration. This setting will cause RTP packets to be saved because the raw packet stream is being transmitted. Set packetbuffer_sender = no or comment out the line to disable packet transmission.

server_type_compress = zstd

(Default: zstd) Compression algorithm for the client/server channel. Options: zstd, gzip, lzo, none.

receiver_check_id_sensor = yes

(Default: yes) Differentiate packets by originating sensor. Set to 'no' for multipath routing scenarios.

Important: Exclude server_bind_port from sipport On central servers in client/server mode, ensure the server_bind_port (default 60024) is excluded from the sipport directive. Including this port causes the sensor-to-server communication traffic to be captured as SIP packets, leading to high and continuously increasing memory utilization.

Example for default server_bind_port = 60024:

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

# CORRECT - excludes sensor communication port:
sipport = 1-60023
sipport = 60025-65535

See Distributed Architecture for more details.

Time Synchronization

mirror_connect_maximum_time_diff_s = 2

(Default: 2) Maximum time difference for mirror connections.

client_server_connect_maximum_time_diff_s = 2

(Default: 2) Maximum time difference for client/server connections.

receive_packetbuffer_maximum_time_diff_s = 30

(Default: 30) Maximum time difference in seconds for packet buffer reception on the central server. Packets older than this threshold are discarded. Adjust this value in distributed setups to control how aggressively the server filters stale packets when client buffers are overloaded.

Legacy Mirroring Model

mirror_bind_ip = 0.0.0.0

The IP the receiver sensor listens on for the unencrypted, legacy mirroring protocol.

mirror_bind_port =

Port for legacy mirroring.

mirror_bind_sensor_id_by_sender = yes

(Default: no) Bind the sensor ID to the sending probe's IP address in mirroring mode. When enabled, packets received from different probes are automatically associated with the corresponding sensor ID configured on each probe. This is useful for distinguishing which probe sent the packets in distributed mirror mode deployments where multiple probes forward traffic to a single receiver.

mirror_destination_ip = 10.0.0.1

The IP of the receiver sensor that the sender should stream packets to.

mirror_destination_port =

Port for mirror destination.

mirror_require_confirmation = yes

(Default: yes) Require packet confirmation. Disable for higher throughput.

mirror_use_checksum = yes

(Default: yes) Enable block-level checksums.

pcap_queue_dequeu_window_length = 2000

(Default: 2000) Window length in ms for sorting packets from multiple mirrors.

Storage & File Management (Spooldir)

Location and Permissions

spooldir = /var/spool/voipmonitor

The primary directory for storing all captured data (PCAP, GRAPH, AUDIO files).

spooldir_rtp =

Separate directory for RTP files.

spooldir_graph =

Separate directory for graph files.

spooldir_audio =

Separate directory for audio files. When set, audio files are saved directly to this directory without the default spooldir date/time nesting structure. Warning: This configuration spawns a separate audio conversion process for every call, which can overload the system with high call volumes. This method is not recommended for deployments with more than 100 concurrent calls. For high-traffic deployments, consider using saveaudio_singlefolder or a scripting workaround to move files from the default spooldir structure.

spooldir_2 = /var/spool/voipmonitor2

Secondary storage directory with separate autoclean setup. This directory is used exclusively for PCAPs from calls that match capture rules where the "Store pcaps to second spooldir" option is enabled. Note: This is NOT an automatic overflow directory when the primary spooldir becomes full. When the primary directory reaches its limit (defined by maxpoolsize or maxpooldays), the cleanspool process triggers and deletes the oldest files from the primary directory to free up space. Standard traffic continues to write to the primary spooldir based on your capture rules. Use this feature to store specific subsets of calls (e.g., VIP customers, legal holds) that require different retention policies (e.g., maxpoolsize_2, maxpooldays_2) than the standard traffic. Important: To allow the GUI to access files stored in spooldir_2, you must also configure the "Sniffer second datapath" setting in the GUI under Settings > System Configuration > Basic and set it to the same path as spooldir_2 in the sensor configuration. Without this GUI setting, the web interface will show "Data not yet written to disk" errors when trying to access recordings stored in the secondary spool directory, even though the files exist on the disk.

spooldir_file_permission = 0666

spooldir_dir_permission = 0777

Allows setting specific filesystem permissions for newly created files and directories.

spooldir_owner = root

spooldir_group = root

Owner and group for created files.

spooldir_by_sensor = no

(Default: no) If enabled, creates subdirectories within the spooldir for each `id_sensor`.

spooldir_by_sensorname = yes

Organize by sensor name instead of ID.

name_sensor = sensor1

Sensor name for directory organization.

cachedir = /dev/shm/voipmonitor

Cache directory for temporary storage. Use RAM or SSD for better performance.

PCAP/TAR Storage Strategy

tar = yes

(Default: yes) This is a key performance feature. Instead of writing thousands of small PCAP files, voipmonitor groups them into minute-based `.tar` archives, which drastically reduces disk I/O load.

tar_maxthreads = 8

(Default: 8) Maximum threads for tar compression.

tar_compress_sip = zstd

(Default: zstd) SIP TAR compression. Options: none, gzip, zstd, lzma.

tar_sip_level_zstd = 1

(Default: 1) Compression level for SIP TAR.

tar_compress_rtp = no

(Default: no) RTP TAR compression. Individual RTP pcaps are compressed with lzo by default.

tar_compress_graph = zstd

(Default: zstd) Graph TAR compression.

tar_graph_level_zstd = 1

(Default: 1) Compression level for graph TAR.

tar_move = yes

(Default: no) Move tar files to another directory after closing. Options: no, yes (move and delete), copy.

tar_move_destination_path = /mnt/nfs/storage

Destination for tar move.

tar_move_max_threads = 2

(Default: 2) Threads for moving tar files.

Saving Options

savesip = yes

Enables saving of SIP packets.

savertp = yes

Controls saving of RTP packets. Options are yes (save full RTP packets), header (save only RTP headers, not the audio payload), or no (do not save RTP packets). savertp = header prevents audio reconstruction but keeps the RTP analysis tool functional in the GUI. savertp = no also disables the RTP analysis tool, but QoS/MOS metrics are still calculated from RTCP packets regardless of the savertp setting.

savertp_video = no

(Default: no) Save video RTP packets. Options: no, yes, header, cdr_only. Important: VoIPmonitor can capture and save only one video RTP stream per call (CDR). If a SIP session negotiates multiple video streams simultaneously, only ONE stream will be saved to the PCAP file. The other video streams will not be captured in the PCAP. This is a system limitation - you cannot capture multiple video streams from a single session to a PCAP file concurrently. As a workaround, you can use savertp_video = cdr_only to capture metadata without storing full video payloads, use custom SIP headers to store SDP attributes in the database for filtering and reporting, or configure call merging to split sessions into separate CDRs if possible. This limitation applies to PCAP file storage. The cdr_rtp table will still show all detected video streams, but only the first one will be present in the PCAP file.

savertcp = yes

Enables saving of RTCP (RTP Control Protocol) packets.

saveudptl = no

(Default: no) Save T.38 fax packets (transported via UDPTL protocol). When enabled, T.38 fax packets are saved to the PCAP file regardless of the savertp setting. This allows viewing T.38 packets in the SIP History ladder diagram and enables TIFF fax image generation from captured calls. Use this option when you want to keep audio RTP streams header-only for space savings (savertp = header or savertp = no) while still capturing fax data for analysis and debugging. Note: If savertp = yes is set, T.38 packets are automatically saved as part of RTP streams and this option is redundant.

savegraph = yes

Enables saving of call graph data.

null_rtppayload = no

(Default: no) Zero out all RTP payload data.

maxpcapsize = 500

(Default: unset) Maximum pcap file size in MB.

Disabling Audio Recording

To prevent VoIPmonitor from recording calls or saving RTP streams (ensuring no audio can be reconstituted), use the following configuration:

savertp = header

CRITICAL: Use header, not no. Setting savertp = header saves RTP headers for QoS statistics and RTP analysis tools but discards the audio payload, preventing audio reconstruction. Using savertp = no will also disable the RTP analysis tool in the GUI.

saveaudio = no

Disables automatic audio file extraction (.wav, .ogg, .mp3).

Complete configuration for no audio recording:

# Disable audio recording - save headers only for statistics
savertp = header
saveaudio = no

ℹ️ Note: If you need to capture T.38 fax packets for display in the SIP History ladder diagram (or for TIFF fax image generation) while keeping audio RTP streams header-only for space savings, add saveudptl = yes to your configuration. This allows fax monitoring without saving full audio RTP payloads.

⚠️ Warning: When using packetbuffer_sender = yes (probe mode), these settings must be applied on the receiving central server, not the probe itself. The probe forwards all packets including RTP to the central server for processing.

⚠️ Warning: If savertcp = yes is enabled, RTCP packets will be stored separately. This may cause the GUI to display audio replay buttons that will fail to play audio, since only RTCP information is available and not the actual RTP payload. Set savertcp = no to prevent this confusion.

Verifying audio recording is disabled:

# Check spool directory sizes - should show minimal growth for RTP/RTPALL
du -h -d1 /var/spool/voipmonitor/ | sort -k2,2

After running calls, the RTP and RTPALL directories should remain small (only headers) and no .wav, .ogg, or .mp3 audio files should be generated.

PCAP Compression

pcap_dump_zip = yes

(Default: yes) Enable file compression for pcap files.

pcap_dump_zip_sip = zstd

SIP compression. Options: no, zstd, gzip, lzo, lz4.

pcap_dump_zip_rtp = lzo

(Default: lzo) RTP compression.

pcap_dump_zip_graph = no

Graph compression.

pcap_dump_ziplevel = 3

(Default: 3) Compression level.

pcap_dump_writethreads = 1

(Default: 1) Initial compression threads. Auto-scales.

pcap_dump_writethreads_max = 32

(Default: 32) Maximum compression threads.

pcap_dump_asyncwrite = yes

(Default: yes) Enable asynchronous writing.

pcap_dump_bufflength = 8184

(Default: 8184) Buffer size in bytes.

Spool Cleaning

cleanspool = yes

(Default: yes) Enables the automatic cleaning process for the spool directory.

cleanspool_enable_fromto = 1-5

(Default: 0-24) Restrict cleaning to specific hours.

maxpoolsize = 102400

(Default: 100 GB) The primary retention setting. Deletes the oldest data hourly until the specified size limit is reached (in MB).

maxpooldays = 30

(Default: unset) An alternative policy that deletes all data older than the specified number of days.

Note: Separate `maxpoolsip*`, `maxpoolrtp*`, `maxpoolgraph*`, `maxpoolaudio*` options exist for granular policies.

autocleanspoolminpercent = 1

(Default: 1%) Emergency cleaning trigger percentage.

autocleanmingb = 5

(Default: 5 GB) Emergency cleaning trigger in GB.

maxpool_clean_obsolete = yes

(Default: no) Clean files not in the index.

Audio File Generation

saveaudio = wav

(Default: no) If enabled, voipmonitor will generate an audio file (`.wav`, `.ogg`, or `.mp3`) for each call in addition to the PCAP file. Options: wav, ogg, mp3, or yes. Using yes will default to WAV format. Note: This is generally not necessary and adds significant CPU/I/O load.

save_audiograph = yes

(Default: no) Enables generation of audio graph files (waveform and spectrogram images) stored in the spooldir/AUDIOGRAPH directory. These graphs visualize audio quality (MOS, jitter, packet loss) without requiring audio playback. If savertp = yes, audio graph files can be generated directly from the PCAP file without needing to enable this option. For auto-cleaning configuration, see maxpoolaudiographsize and maxpoolaudiographdays.

audiograph_fftw_fork_mode = no

(Default: yes) Controls the FFTW (Fastest Fourier Transform) library's threading mode for audiograph generation. Setting to no disables the fork-based thread pool, preventing memory leaks in the sensor process. Use this setting if you experience intermittent audiograph generation failures or sensor crashes. This option resolves issues where audiographs become unavailable in the GUI due to process instability.

audiograph_ms_per_pixel = 0

(Default: variable) Controls the horizontal resolution of the audiograph waveform by specifying milliseconds of audio per pixel. Lower values produce higher resolution waveforms (more pixels per second of audio), while higher values reduce detail. Setting to 0 enables maximum resolution for the highest quality saved audiograph images, matching the quality generated on-demand by the audio player. Adjust this value if you notice significant quality differences between saved audiograph images and the audio player visualization. Tradeoff: higher resolution requires more disk space and processing time.

audiograph_spectrogram_height = 64

(Default: variable) Controls the height (in pixels) of the spectrogram portion of the audiograph. Increasing this value produces taller and more detailed spectrograms, while decreasing it saves disk space and reduces generation time. Set to 64 or higher for high-quality saved audiograph images. The spectrogram height affects only the saved image files; on-demand audio player generation may use different defaults. Adjust together with audiograph_ms_per_pixel to match the quality generated by the audio player.

saveaudio_singlefolder = /var/spool/voipmonitor/audio

(Default: unset) Store all generated audio files in a dedicated directory separate from the main PCAP spooldir structure. Audio files are organized under the specified path with date-based subdirectories (e.g., /var/spool/voipmonitor/audio/2025/01/05/), which makes it easier to isolate audio storage for separate backup, mounting, or management purposes. This is the recommended approach for separating audio storage while maintaining organized directory structure. Prerequisite: saveaudio must be enabled (set to wav, ogg, mp3, or yes).

saveaudio_afterconnect = no

(Default: no) Store audio only for connected calls.

saveaudio_from_first_invite = yes

(Default: yes) Generate silence from first INVITE to match SIP signalization length.

saveaudio_stereo = yes

(Default: yes) Caller in left channel, called in right channel.

mp3_quality = 5

(Default: 5) MP3 quality (0-9, 9 is worst).

ogg_quality = 0.4

(Default: 0.4) OGG quality setting.

audioqueue_threads_max = 10

(Default: 10) Maximum audio processing threads.

curl_hook_wav = http://127.0.0.1:8080/your-script-path

Webhook URL called for each audio file.

Real-Time Call Notifications (SendCallInfo)

💡 Tip: This feature enables integration with external systems such as CRMs, helpdesk tickets, or custom dashboards by sending call information in real-time.

The `SendCallInfo` feature sends real-time call notifications to a remote URL before the call ends and before the CDR is stored in the database. This allows external systems to receive call information as it happens, based on SIP packets.

SendCallInfo = yes

(Default: no) Enable real-time call notifications to an external URL. When enabled, VoIPmonitor sends HTTP requests to the configured destination URL as calls are detected.

SendCallInfoUrl = http://your-api-server.com/endpoint

Destination URL where call information will be sent. The URL must be reachable from the VoIPmonitor server.

SendCallInfoMethod = post

(Default: post) HTTP method to use for sending call information. Supported methods are `post`, `get`, and `json`.

SendCallInfoContentType = application/json

(Default: application/json) Content-Type header for the HTTP request. Configure this based on your external API requirements.

⚠️ Warning: The HTTP request is sent based on SIP packet information during the call, not after the call completes. Final call duration and termination data will not be included in the notification.

Email SMTP Configuration

email_smtp_server = localhost

(Default: unset) SMTP server address for sending notification emails from the sniffer. When configured, the sniffer uses this server for any email-based alerts or notifications. If not needed, leave this option unset or comment it out to avoid connection attempts overhead. If you experience slow performance or delays in CDR processing, especially when processing PCAP files from a directory, consider commenting out this setting as it may cause thread blocking during SMTP connection attempts.

Call Processing & Protocol Logic

Call Identification & Merging

remoteparty_caller = calling, `passertedidentity = no`, etc.

A group of options that control which SIP headers are used to determine the caller/callee information. See Caller/Called Identity Configuration.

sipoverlap = yes

(Default: yes) Allows the destination number to be updated from subsequent INVITEs within the same dialog, necessary for overlap dialing.

matchheader = in-reply-to

Uses the specified SIP header to link different call legs into a single related call in the GUI.

callidmerge_header = Parent-Call-ID

A more advanced method to merge call legs based on a shared identifier in a custom header.

callidmerge_secret = yourSecretString

XOR secret for encrypted Call-ID merging header.

call_id_alternative = Session-ID,Join

Alternative unique identifiers for call merging (e.g., Cisco CUCM).

cdrproxy = yes

(Default: yes) Track all proxy IPs in `cdr_proxy` table.

Call Timeouts & Termination

absolute_timeout = 14400

(Default: 4 hours) Forcefully ends any call that lasts longer than this value to prevent runaway processes. Sets `cdr.bye = 102`.

rtptimeout = 300

(Default: 5 minutes) Closes a call if no RTP or RTCP packets have been received for this duration.

sipwithoutrtptimeout = 3600

(Default: 1 hour) Closes a SIP call that has no associated RTP stream after this duration.

bye_timeout = 1200

(Default: 1200) Timeout in seconds after BYE message.

bye_confirmed_timeout = 600

(Default: 600) Timeout after confirmed BYE.

onewaytimeout = 15

(Default: 15) Ends call if no reply from other side. Sets `cdr.bye = 101`.

ignore_rtp_after_response = 408;480;486;487;481;600;503

(Default: as shown) A list of SIP final response codes after which the sniffer should stop looking for RTP for that call.

ignore_rtp_after_bye = no

(Default: no) Stop RTP processing after BYE.

ignore_rtp_after_bye_confirmed = yes

(Default: yes) Stop RTP processing after confirmed BYE.

ignore_rtp_after_cancel_confirmed = yes

(Default: yes) Stop RTP processing after confirmed CANCEL.

redirect_response_300_timeout = 300

(Default: 300) Timeout for SIP 300 redirect.

get_reason_from_bye_cancel = yes

(Default: yes) Fetch Q.850 Reason header from BYE/CANCEL.

ignore_duration_after_bye_confirmed = yes

(Default: yes) Set duration based on confirmed BYE.

detect_alone_bye = no

(Default: no) Flag CDR if BYE is alone in dialog. Warning: Can cause high DB load.

Source Code Configuration (Advanced)

The following timeout values are configured at compile time by modifying the sniffer source code and recompiling. These are not available as configuration file options. To change them:

1. Download the sniffer source code from GitHub:

cd /usr/src
git clone -b master https://github.com/voipmonitor/sniffer.git
cd sniffer

1. Locate and modify the constant definition:

destroy_call_at_bye

Timeout in seconds after BYE packet before stopping call interception. Edit the constant definition in call_table.cpp and set the desired value (e.g., 1200 for 20 minutes).

1. Recompile the sniffer:

./configure
make
make install
systemctl restart voipmonitor

This forces the sniffer to stop intercepting a call after the specified timeout following a BYE packet, even if RTP streams are still active.

RTP Processing

jitterbuffer_f1 = yes

(Default: yes) Fixed 50ms jitterbuffer simulation, saved in cdr.[ab]_f1.

jitterbuffer_f1_jbsize = 50

(Default: 50) Jitter buffer size in ms.

jitterbuffer_f2 = yes

(Default: yes) Fixed 200ms jitterbuffer simulation, saved in cdr.[ab]_f2.

jitterbuffer_adapt = yes

(Default: yes) Adaptive jitterbuffer up to 500ms.

Behavior: By default (yes), MOS is calculated and counted. CPU-intensive; disable some on resource-constrained systems. Setting to no skips MOS calculation and pushes static value 4.5 to GUI. Setting to null skips calculation and pushes '-' (NULL) to GUI. Disabling calculation saves CPU time on heavily loaded hosts.

mosmin_f2 = yes

(Default: yes) Calculate mos_min_mult10 only from f2 jitter simulator.

Note for CPU optimization: If you experience high CPU load on RTP processing threads during peak call volume, you can significantly reduce CPU consumption (approximately 30%) by disabling MOS calculations for f1 and adaptive jitterbuffer while keeping f2 MOS calculation active. Configure as follows

mosf1 = no

(Default: yes) Calculate MOS for jitterbuffer_f1. Disabling saves CPU on RTP threads.

mosf2 = yes

(Default: yes) Calculate MOS for jitterbuffer_f2 (static 200ms jitter). This provides a stable MOS metric even when f1/adapt are disabled.

mos_adapt = no

(Default: yes) Calculate MOS for adaptive jitterbuffer. Disabling provides additional CPU savings.

RTP Tracking & SDP

sdp_multiplication = 3

(Default: 3) How many calls can share same IP:port. 0 = only newest call.

disable_process_sdp = no

(Default: no) Disable SDP processing. Only for very high CPS (>1000).

rtp_check_both_sides_by_sdp = no

(Default: no) Eliminate RTP duplication by checking source IP:port. Options:

• no: Disabled (default)
• yes: Verify both sides per SDP
• keep_rtp_packets: Same as 'yes' but store unverified packets for debugging
• strict: Allow unverified packets until first verified packet arrives
• very_strict: No unverified packets allowed at any time

ignore_rtp_after_auth_failed = yes

(Default: yes) Close RTP ports on authentication failure.

disable_rtp_seq_probation = no

(Default: no) Disable RFC 3550 sequence validation.

allow-zerossrc = no

(Default: no) Allow RTP packets with zero SSRC. Some VoIP gateways or PBX systems may send RTP packets with an SSRC (Synchronization Source) value of zero during specific scenarios such as silence periods, hold states, or certain codec configurations. By default VoIPmonitor drops these packets because a zero SSRC does not typically indicate a valid RTP stream. If you observe calls with missing audio during silence or apparent "dropped" RTP packets, enable this option. This setting is particularly useful when monitoring specific legacy or non-standard VoIP equipment that uses zero SSRC values.

check_diff_ssrc_on_same_ip_port = yes

(Default: yes) Check for different SSRC on same IP:port.

save_sdp_ipport = yes

(Default: yes) Store SDP IP/port in `cdr_sdp` table.

rtpfromsdp_onlysip = no

(Default: no) Only use RTP streams with same IP as SIP header.

rtpip_find_endpoints = yes

(Default: yes) Determine actual RTP endpoints (not proxies).

SRTP (Encrypted Media)

See SRTP Configuration section above.

NAT Handling

natalias = 1.1.1.1 10.0.0.3

Creates a mapping between a public IP and a private IP, helping the sniffer correctly associate call legs behind a NAT device. Multiple lines can be used.

sdp_reverse_ipport = no

(Default: no) Enable reverse IP:port sniffing for NAT scenarios. Use with caution.

sdp_ignore_ip = 192.168.0.1

Ignore RTP streams from specific IPs.

sdp_ignore_ip_port = 192.168.0.1:100

Ignore RTP streams from specific IP:port.

SIP REGISTER, OPTIONS, SUBSCRIBE, NOTIFY

sip-register = no

(Default: no) Enables the processing and storage of SIP `REGISTER` messages. Options: yes, nodb, no.

save-sip-register = no

(Default: no) Save REGISTER messages to disk.

sip-register-timeout = 5

(Default: 5) Timeout in seconds for REGISTER reply.

sip-register-active-nologbin = yes

(Default: yes) Skip binary logging for REGISTER active table.

sip-register-max-registers = 4

(Default: 4) Max request packets before terminating register session.

sip-register-max-messages = 20

(Default: 20) Max total packets before terminating register session.

sip-register-state-timeout = 600

(Default: 600) Interval between saving same states.

sip-register-state-compare-digest_ua = no

(Default: no) When enabled with yes, the sniffer will create a new record in the register state table whenever the SIP User-Agent (UA) string changes, even if other registration details remain the same. The alias sip-register-state-compare-ua = yes can also be used. This allows detection of UA changes by querying the database, but does not trigger a native GUI alert. Use with the anti-fraud system or custom database queries for detection.

sip-options = no

(Default: no) Enables the processing of SIP `OPTIONS` messages.

save-sip-options = no

(Default: no) Save OPTIONS to disk.

sip-subscribe = no

(Default: no) Enable SUBSCRIBE processing.

sip-notify = no

(Default: no) Enable NOTIFY processing.

sip-message = yes

(Default: yes) Enables processing for SIP `MESSAGE` requests.

SIP History for Requests

save_sip_history = no

(Default: no) Enables storage of SIP signaling in the database. Multiple options are available depending on your needs:

• no (default) - No SIP history stored
• requests - Stores ALL SIP request methods (PUBLISH, INFO, UPDATE, PRACK, REFER, etc.) in the sip_request table, enabling GUI filtering with the "SIP requests" dropdown
• responses - Stores SIP response text for full-text searching, enabling the "SIP responses" filter in CDR view
• all - Stores both requests and responses (combined)
• requests,responses - Explicitly stores both requests and responses

Warning: Enabling SIP history significantly increases database write load and storage size, especially in high-traffic environments. Only enable options you need for your troubleshooting or reporting requirements.

Example usage for PUBLISH packets:

• By default, SIP PUBLISH packets are captured but not stored in the database or indexed for GUI filtering
• To make PUBLISH and other non-call requests searchable, set save_sip_history = requests
• After processing new calls, the GUI "SIP requests" filter will show all observed request types
• Restart the voipmonitor service to apply changes

Example usage for SIP response text searching:

• The standard "Last SIP Response" filter only searches numeric response codes (e.g., 503, 404)
• To search full SIP response text (e.g., "Service Unavailable", custom SBC messages), set save_sip_history = responses
• After processing new calls, the GUI "SIP responses" filter field in the CDR view becomes active
• You can then search for specific text patterns in SIP response headers
• Restart the voipmonitor service to apply changes

save_sip_responses = yes

(Default: no) Alternative option to save_sip_history = responses. Enables storage of SIP response text for searching in the CDR GUI. Use this if you only need response text storage without request history. Enable either this option or save_sip_history = responses, but not both.

CDR Processing

nocdr = no

(Default: no) Disable saving CDRs to MySQL.

cdronlyanswered = no

(Default: no) Only save answered calls.

cdronlyrtp = no

(Default: no) Only save calls with RTP.

cdr_check_exists_callid = no

(Default: no) Check for existing CDR with same Call-ID and update it instead of creating a duplicate row. Use this when multiple probes or sniffer processes capture the same call packets and write CDRs to a shared database. The MySQL user must have UPDATE privileges on the cdr table. Side effect: the final CDR will only be associated with the id_sensor of the sniffer that last processed the call.

cdr_ignore_response = 302,303,4

Ignore CDRs based on SIP response codes. Use '0' or '000' to filter unreplied INVITE requests (calls with no response). This setting must be applied on the sniffer that analyzes and stores the packets. It will not work on a mirroring sniffer or probe where packetbuffer_sender=yes is set.

cdr_sip_response_number_max_length = 3

Limit phone number length in SIP response text.

cdr_sip_response_normalisation = yes

(Default: yes) Normalize SIP response text.

cdr_reason_string_enable = yes

(Default: yes) Store reasons in cdr_reason table.

cdr_reason_normalisation = yes

(Default: yes) Normalize reason text.

cdr_ua_enable = yes

(Default: yes) Store user agent in cdr.a_ua and cdr.b_ua.

cdr_ua_normalisation = yes

(Default: yes) Normalize user agent strings.

cdr_stat = both

Enable aggregated CDR statistics. Options: both, src, dst.

cdr_stat_interval = 15

(Default: 15) Statistics interval in minutes.

vlan_siprtpsame = no

(Default: no) Filter RTP by VLAN tag from SIP packet.

dscp = yes

(Default: yes) Store DSCP values in cdr.dscp.

Custom Headers

custom_headers = Referred-By, Diversion, X-Custom-Header

(Default: unset) Specifies custom SIP headers to capture and store in the database. Multiple headers are separated by commas. After adding headers to this directive and restarting the sniffer, corresponding database columns are automatically created in the `cdr_next_X` tables. You can then configure the display and filtering behavior in the GUI under Settings > CDR Custom Headers. Common use cases include capturing headers like Referred-By, Diversion, or custom correlation identifiers for call tracing.

custom_headers_last_value = yes

(Default: yes) Use last occurrence of custom header. If set to no, the first occurrence in the SIP message is stored instead.

custom_headers_max_size = 1024

(Default: 1024) Maximum custom header size in bytes. Headers longer than this value will be truncated.

allow_missing_header = no

(Default: no) Write empty value if header is missing in the first SIP packet of the call.

Call Recording Control

pauserecordingdtmf = *9

(Default: unset) If set, RTP recording will be paused when this DTMF sequence is detected in a call.

pauserecordingdtmf_timeout = 4

(Default: 4) Timeout between DTMF digits in seconds.

pauserecordingheader = MyCustomPauseHeader

(Default: unset) Pauses/unpauses recording based on the presence of a specific SIP header and its value (e.g., `pause` or `unpause`).

norecord-header = yes

(Default: no) If any SIP packet in a call contains the `X-VoipMonitor-norecord` header, the entire call record (PCAP and CDR) will be discarded.

norecord-dtmf = yes

(Default: no) Delete recording if DTMF sequence "*0" is detected.

182queuedpauserecording = no

(Default: no) Pause on "182 Queued avaya-cm-data".

Audio Analysis

dtmf2db = no

(Default: no) Store DTMF to database (SIP INFO and RTP RFC).

inbanddtmf = no

(Default: no) Enable in-band DTMF detection. G711 only. CPU intensive.

silencedetect = no

(Default: no) Enable silence detection. G711 only. CPU intensive.

silencethreshold = 512

(Default: 512) Silence detection threshold.

clippingdetect = no

(Default: no) Enable clipping detection. G711 only.

fasdetect = no

(Default: no) FAS (False Answer Supervision) detection based on ring detection after 200 OK.

save-energylevels = no

(Default: no) Store average 16-bit energy levels for each RTP packet in `cdr_rtp_energylevels` table.

energylevelheader = X-energlvl

Only save energy levels for calls with this header.

sipalg_detect = no

(Default: no) Detect SIP-ALG usage on routers/firewalls.

MOS Scoring

mosf1 = no

(Default: yes) Calculate MOS for jitterbuffer_f1 (50ms fixed jitterbuffer). Disabling saves CPU on RTP threads.

mosf2 = yes

(Default: yes) Calculate MOS for jitterbuffer_f2 (200ms fixed jitterbuffer). This provides a stable MOS metric.

mos_adapt = no

(Default: yes) Calculate MOS for adaptive jitterbuffer (up to 500ms). Disabling provides CPU savings.

CPU Optimization Note: If you experience high CPU load on RTP processing threads during peak call volume, you can reduce CPU consumption by approximately 30% by disabling MOS calculations for f1 and adaptive jitterbuffer while keeping f2 MOS calculation active

mosf1 = no

mos_adapt = no

This configures VoIPmonitor to compute MOS only for the static 200ms jitter (f2), providing a quality metric with minimal CPU overhead.

mos_g729 = no

(Default: no) Enable G.729 specific MOS scoring. Max MOS 3.92 for perfect G.729 calls.

ignorertcpjitter = 0

(Default: 0) Ignore RTCP jitter values higher than this.

ignore_mos_degradation_for_contiguous_packet_loss_greater_than = 1024

(Default: 1024) Don't count consecutive packet loss above this threshold.

ignore_mos_degradation_in_rtp_pause_without_seq_gap = 1000

(Default: 1000) Don't lower MOS for RTP gaps without sequence gaps.

plcdisable = no

(Default: no) Disable Packet Loss Concealment.

PESQ MOS

mos_lqo = no

(Default: no) Enable ITU-T P.862 PESQ scoring. Requires licensed pesq binary.

mos_lqo_bin = pesq

Path to PESQ binary.

mos_lqo_ref = /path/to/reference.wav

Reference audio file for PESQ.

Other Protocols

skinny = yes

(Default: no) Enables parsing for Cisco Skinny Call Control Protocol (SCCP).

skinny_port = 2000

(Default: 2000) Skinny port(s).

skinny_ignore_rtpip = 10.1.1.1

Ignore RTP from Cisco Call Manager IP.

mgcp = yes

(Default: no) Enables parsing for MGCP.

tcp_port_mgcp_gateway = 2427

udp_port_mgcp_gateway = 2427

tcp_port_mgcp_callagent = 2727

udp_port_mgcp_callagent = 2727

ss7 = yes

(Default: no) Enables parsing for SS7-over-IP (SIGTRAN).

ss7_rudp_port = 7000

SS7 RUDP port.

ss7_use_sam_subsequent_number = yes

Use SAM subsequent number.

diameter = no

(Default: no) Enables parsing for the Diameter protocol.

diameter_tcp_ports = 3868

diameter_udp_ports = 3868

diameter_time_overlap = 10

(Default: 10) Allow Diameter packets up to 10 seconds before SIP sessions.

diameter_ignore_domain = no

(Default: no) Skip domain match between SIP and Diameter.

diameter_ignore_prefix = no

(Default: no) Allow 'sip:' to match 'tel:' prefix.

ipv6 = yes

(Default: no) Enable IPv6 support. Database must be created with IPv6 columns.

IPFIX Support

IPFIX (IP Flow Information Export) allows receiving RTP QoS data from Oracle/ACME SBCs and other exporters.

ipfix = yes

(Default: no) Enable IPFIX collector.

ipfix_bind_ip = 0.0.0.0

(Default: 0.0.0.0) Address to bind IPFIX UDP collector.

ipfix_bind_port = 12345

UDP port to listen for IPFIX.

ipfix_qos_fill_rtp_streams = yes

(Default: no) Save all observed RTP streams into `cdr_rtp`.

ipfix_qos_fill_codec = yes

(Default: no) Persist exporter-provided codec value.

ipfix_qos_fill_jitter = yes

(Default: no) Persist RTP/RTCP jitter values.

Important: Monitoring SIPS/SRTP Calls When using IPFIX to monitor call quality for encrypted SIP (SIPS) and RTP (SRTP) traffic, ensure the TLS port is included in the sipport configuration. For example:

# Include both UDP and TLS SIP ports
sipport = 5060,5061

This allows VoIPmonitor to properly associate IPFIX QoS data with SIPS endpoints.

Data written to CDR:

• a_saddr / b_saddr: RTP source IPs
• a_received / b_received: Total RTP packets
• a_lost / b_lost: Lost RTP packets
• a_mos_f2_mult10 / b_mos_f2_mult10: MOS values (multiplied by 10)

SIPREC Support

SIPREC enables VoIPmonitor to act as a recording server for SIP proxies like OpenSIPS.

siprec_bind = 0.0.0.0

IP address to bind SIPREC server. Required to enable SIPREC.

siprec_bind_port = 5099

Port to listen for SIPREC connections. Required to enable SIPREC.

siprec_rtp_min = 10000

(Default: 10000) Lower bound of RTP port range.

siprec_rtp_max = 20000

(Default: 20000) Upper bound of RTP port range.

siprec_rtp_stream_timeout_s = 300

(Default: 300) RTP stream timeout in seconds.

siprec_rtp_streams_max_threads = 2

(Default: 2) Maximum RTP reception threads.

siprec_rtp_streams_max_per_thread = 100

(Default: 100) Maximum streams per thread.

HEP Support

HEP (Homer Encapsulation Protocol) allows receiving SIP traffic mirrored from Kamailio, OpenSIPS, Asterisk, and other SIP proxies.

receiver_mode = yes

(Default: no) Required to enable the HEP receiver. This directive must be set to yes in the [general] section before the HEP collector will bind to the configured port and accept HEP packets. Without receiver_mode = yes, the sensor will not listen on hep_bind_port even if hep = yes is set. After enabling, verify the port is listening with netstat -an | grep hep_bind_port.

hep = yes

(Default: no) Enable HEP collector.

hep_bind_ip = 0.0.0.0

(Default: 0.0.0.0) Address to bind HEP UDP collector.

hep_bind_port = 9060

UDP port to listen for HEP packets.

hep_bind_udp = yes

(Default: yes) Enable UDP binding for the HEP collector. This directive allows the HEP receiver to bind to a UDP port. Set to no only if you need to disable UDP binding for specific network configurations. In most deployments, this should be left at the default yes.

hep_kamailio_protocol_id_fix = yes

(Default: yes) Workaround for Kamailio protocol ID issues. Enable this when receiving HEP from Kamailio.

Whisper Transcription

VoIPmonitor supports audio transcription using OpenAI's Whisper model.

audio_transcribe = yes

(Default: no) Enable audio transcription.

whisper_rest_api_url = http://localhost:9000/asr?output=json&encode=true

URL for Whisper REST API. If set, overrides native and python methods.

whisper_rest_api_mode = stereo

(Default: stereo) REST API mode: 'stereo' (one stereo WAV) or 'split' (two mono WAVs).

whisper_native = no

(Default: no) Use native whisper.cpp library.

whisper_model = /path/to/ggml-base.en.bin

Path to Whisper model file.

whisper_language = auto

(Default: auto) Language for transcription. 'auto' for automatic detection.

whisper_timeout = 60

(Default: 0) Timeout for python script execution.

whisper_deterministic_mode = no

(Default: no) Enable deterministic mode.

whisper_python = /usr/bin/python3

(Default: python3) Path to Python interpreter.

whisper_threads = 4

(Default: 0, auto) Number of Whisper processing threads.

whisper_native_lib = /usr/local/lib/libwhisper.so

Path to native Whisper library.

audio_transcribe_threads = 2

(Default: 2) Number of transcription processing threads.

audio_transcribe_queue_length_max = 1000

(Default: 1000) Maximum transcription queue length.

audio_transcribe_parallel_channel_processing = yes

(Default: yes) Process audio channels in parallel.

Kamailio Mirroring

Configuration for receiving SIP traffic mirrored from Kamailio's siptrace module.

receiver_mode = yes

(Default: no) Enables the receiver mode for receiving mirrored traffic. When using Kamailio mirroring or the HEP collector, this directive must be set to yes in the [general] section. Without this setting, the sensor will not bind to the configured receiver port and will not receive traffic, regardless of other configuration settings. Always verify the service is listening on the expected port after enabling this option using netstat -an | grep 5888 or ss -ulpn | grep voipmonitor.

Kamailio configuration:

loadmodule "siptrace.so"
modparam("siptrace", "trace_on", 1)
modparam("siptrace", "duplicate_uri", "sip:10.0.0.1:5888")
modparam("siptrace", "trace_to_database", 0)
modparam("siptrace", "trace_mode", 4)
modparam("siptrace", "xheaders_write", 1)

kamailio_port = 5888

Port to receive Kamailio mirrored traffic.

kamailio_dstip = 10.0.0.1

VoIPmonitor host IP address.

kamailio_srcip = 10.0.0.2

Kamailio server IP address (optional).

kamailio = no

(Default: no) Enable Kamailio-style substitution on sniffed traffic.

hep_kamailio_protocol_id_fix = yes

(Default: yes) Workaround for Kamailio protocol ID issues.

Ribbon SBC Mirroring

Support for Ribbon SBC monitoring profiles.

Passive Sniffing (Mode 1)

ribbonsbc = yes

(Default: no) Enable Ribbon-style IP:port substitution on sniffed traffic.

ribbonsbc_port = 9514

Expected mirror port in packets (legacy filter).

ribbonsbc_dstip = 10.0.0.1

VoIPmonitor host IP (legacy filter).

ribbonsbc_srcip = 10.0.0.2

Ribbon SBC IP (legacy filter).

Active Listener (Mode 2)

ribbonsbc_bind_ip = 0.0.0.0

Listen address for active mode.

ribbonsbc_bind_port = 9514

Listen port for active mode.

ribbonsbc_bind_udp = no

(Default: no) Enable UDP support. TCP recommended.

ribbonsbc_size_header = yes

(Default: yes) Expect 2-byte size header before each frame.

ribbonsbc_strict_check = no

(Default: no) Only process frames complete per size header.

ribbonsbc_counter_log = no

(Default: no) Log counts of incoming Ribbon frames.

Traffic Dumper

Save captured traffic to PCAP files with optional filtering.

traffic_dumper_path = /var/spool/voipmonitor/traffic

Path where pcap files will be saved. Setting this enables the traffic dumper.

traffic_dumper_by_interface = no

(Default: no) Create separate files per interface (yes) or per DLT type (no).

traffic_dumper_force_flush = no

(Default: no) Force flush after each packet. Impacts performance.

traffic_dumper_filter_ip = 192.168.1.100, 10.0.0.0/8

Filter by IP addresses or networks.

traffic_dumper_filter_port = 5060, 5061, 10000-20000

Filter by ports or port ranges.

Expert & Debugging Options

Warning: These options should only be changed if you are an expert or instructed to do so by the support team.

database_backup_from_date = 2023-01-01

A family of options that puts the sniffer into a special database backup/migration mode, copying data from another database.

coredump_filter = 0x7F

(Default: 0x7F) Controls what memory segments are included in a coredump file if the application crashes.

abort_if_heap_full = no

A set of options that control whether the sniffer should intentionally crash under certain high-load error conditions to generate a coredump for debugging.

interrupts_counters = yes

(Default: yes) Enable interrupt statistics. Disable on Virtuozzo containers.

callslimit = 0

(Default: 0, unlimited) Maximum concurrent calls to process.

skipdefault = yes

(Default: no) Ignore all SIP calls unless capture rules are set.

openfile_max = 65535

(Default: 65535) Maximum open files.

convertchar = :

Replace characters with underscores in filenames.

fbasenameheader = X-custom-filename

Name pcap files based on custom SIP header.

pcapcommand = echo %pcap% >> /tmp/list

Command to run after pcap is closed. Warning: Resource intensive.

filtercommand = myscript '%callid%' '%dirname%'

Command for calls matching capture rules.

printinsertid = no

(Default: no) Print CDRID to stdout on every insert.

DPDK Configuration

dpdk_timer_reset_interval = 60

(Default: 60) Reset interval in seconds.

dpdk_nb_rxq = 2

(Default: 2) Number of receive queues. Increase for higher traffic.

dpdk_rxq_per_thread = no

(Default: no) Process RX queues with separate threads.

dpdk_ignore_ierrors = no

(Default: no) Ignore ierrors (packets with bad checksums).

AI Summary for RAG

Summary: This document is a comprehensive reference guide for the `voipmonitor.conf` sniffer configuration file. It covers General Settings (sensor ID, timezone, watchdog), Deprecated and Removed Configuration Options (for sniffer version 2025.09.1 and later, removed options include: `vxlan`, `vxlan_port`, `vxlan_skipcrc`, `packet_buffer_total_size`, `udp_reassembly`, `udp_reassembly_max_size`, `sipdefrag`, `sipdefrag_maxpacket`, `defragment_max_size`, `defragment_timeout`, `ignore_sip_parsing_errors`, `sip_auto_clean`, `max_sip_size`, `sip_force_content_length`, `sanity_checks`, `check_sip_header`, `interface_snaplen`; modern replacements include `udp_port_vxlan`, `snaplen`, `udpfrag`, `auto_enable_use_blocks`, `deduplicate`), Database Connection and Performance (MySQL settings, partitioning, queue tuning, cleaning, SSL/TLS, and mysqlloadconfig=yes for loading configuration from database including the critical manager_key from the system table; setting mysqlloadconfig=no prevents loading the manager_key and causes "failed read rsa key" startup errors), Network Interface and Sniffing (interface selection, BPF filters, tunneling protocols including TZSP, L2TP, VXLAN, AudioCodes, IPFIX, HEP, and packet deduplication and RTP association with options like `deduplicate`, `auto_enable_use_blocks`, and `deduplicate_ipheader`), Shared Server Optimization (voice breakage and call lag when sniffer shares PBX server, solutions: specify specific interfaces instead of `any`, disable `interfaces_optimize=no`, reduce load with `savertp=header` and `saveaudio=no`), SIP TLS/SSL Decryption (ssl, ssl_ipport, keylogger support), SRTP Configuration (srtp_rtp, ssl_dtls_boost), Caller/Called Identity (remoteparty, passertedidentity, destination_number_mode), Performance and Threading (NUMA, scheduling, buffer configuration), Distributed Architectures (client/server model and legacy mirroring including `mirror_bind_sensor_id_by_sender` for distinguishing sending probes), Storage Management (spooldir, TAR files, pcap saving, compression, and cleaning rules), Call Processing (timeouts, RTP tracking, NAT handling, custom headers, call recording control for privacy and opt-out scenarios including pauserecordingdtmf to pause recordings via DTMF sequences during calls, norecord-dtmf to delete recordings, norecord-header for SIP header-based recording suppression, and pauserecordingheader for pause/unpause via SIP headers ), Audio and Video Packet Saving (savertp for audio RTP payload, savertp_video for video RTP streams such as VP8, VP9, and H.264, savertcp for RTCP, saveaudio for audio file extraction, savegraph for call graphs), SIP Method Processing (REGISTER, OPTIONS, SUBSCRIBE, NOTIFY, MESSAGE, and `save_sip_history` for storing ALL SIP requests including PUBLISH, INFO, UPDATE, PRACK, REFER to enable GUI filtering), Audio Analysis (DTMF, silence detection, energy levels, MOS scoring), Scan PCAP Directory Mode (scanpcapdir for processing pcap files from a directory instead of live capture; useful for monitoring from Windows hosts without SPAN ports using tcpdump to capture and transfer pcaps to VoIPmonitor server), Protocol Support (SIP, Skinny, MGCP, SS7, Diameter), IPFIX Support, SIPREC Support, Whisper Transcription, Kamailio Mirroring, Ribbon SBC Mirroring, and Traffic Dumper.

Keywords: voipmonitor.conf, configuration, sniffer config, sensor, database, mysql, mariadb, cdr_partition, cleandatabase, interface, sniffing, promisc, bpf, filter, tunneling, DPDK, performance, threading, client/server, distributed, remote sensor, spooldir, storage, pcap, tar, maxpoolsize, saveaudio, SIP, RTP, SRTP, DTLS, ssl_dtls_boost, skinny, MGCP, SS7, diameter, NAT, natalias, call recording, watchdog, sched_pol_auto, deduplicate, auto_enable_use_blocks, deduplicate_ipheader, ip_only, packet deduplication, duplicate packets, rtp association, wrong call leg, different nic, different vlan, multiple interface, ssl, ssl_ipport, TLS decryption, IPFIX, SIPREC, whisper, transcription, Kamailio, Ribbon SBC, traffic dumper, energy levels, DTMF detection, silence detection, MOS scoring, call merging, callidmerge_header, rtp_check_both_sides_by_sdp, cdr_summary, cdr_summary_interval, cleandatabase_cdr_summary, aggregation, dashboard performance, custom_headers, custom SIP headers, Referred-By, Diversion, CDR custom headers, capture SIP headers, SIP header filtering, shared server, PBX, resource contention, voice breakage, call lag, interfaces_optimize, dedicated threads, specific interfaces, ethtool, RTP engine, save_sip_history, SIP requests filter, PUBLISH, INFO, UPDATE, PRACK, REFER, non-call SIP methods, GUI SIP requests, mysqlloadconfig, manager_key, failed read rsa key, sensor_conf table, system table, pauserecordingdtmf, norecord-dtmf, norecord-header, pauserecordingheader, privacy, opt-out, call recording control, pause recording, stop recording, DTMF control, SIP header control, video, video RTP, video codec, VP8, VP9, H.264, H264, WebRTC video, savertp_video, video capture, recording video, video packet saving, SSRC, Synchronization Source, zero SSRC, allow-zerossrc, missing audio, silence packets, dropped RTP packets, t2_boost, high traffic threading, defrag thread, reassembly thread, MEMORY IS FULL, threading model, CPU bottleneck, 100% CPU, defrag bottleneck, packetbuffer, high throughput, scanpcapdir, scanpcapmethod, directory mode, offline processing, tcpdump, windows host, without span port, no port mirroring, pcap files, remote capture, deprecated options, deprecated configuration, removed options, legacy options, 2025.09.1, upgrade, vxlan, packet_buffer_total_size, udp_reassembly, sipdefrag, defragment, ignore_sip_parsing_errors, sip_auto_clean, max_sip_size, sanity_checks, check_sip_header, interface_snaplen, udp_port_vxlan, cdr_country_code, caller_country, called_country, country flags, CDR country filtering, country lookup, country code detection

Key Questions:

• What does mysqlloadconfig=no do in voipmonitor.conf?
• Why does the sniffer fail to start with "failed read rsa key" error?
• How does mysqlloadconfig affect loading of the manager_key from the database?
• What are the most important settings in voipmonitor.conf for a new installation?
• How do I configure the database connection for the sniffer?
• How do I fix voice breakage and call lag when the VoIPmonitor sniffer runs on the same server as the PBX?
• What happens when I use interface = any versus specific interface names?
• How can I reduce CPU load on RTP processing threads during peak call volume?
• How do I disable MOS calculations for f1 and adaptive jitterbuffer?
• What configuration saves approximately 30% CPU on RTP threads?
• How does interfaces_optimize affect performance on shared servers?
• What should I do if moving the VoIPmonitor sensor to a separate server is not possible?
• How does specifying multiple interfaces create dedicated threads?
• How do I set up a distributed client/server architecture?
• What is the difference between `packetbuffer_sender = yes` and `no`?
• How do I tune the database for high performance?
• How do I configure the sniffer to listen on multiple SIP ports?
• What are the `maxpoolsize` and `cleandatabase` options and how do they work?
• How do I enable SRTP decryption and what is ssl_dtls_boost?
• How do I configure VoIPmonitor to handle tunneled traffic from a Mikrotik router or AWS?
• How do I pause call recording during a call using DTMF sequences for opt-out scenarios?
• How do I configure pauserecordingdtmf to allow callers to pause recording by pressing a DTMF sequence?
• What is pauserecordingdtmf_timeout and how does it affect DTMF sequence recognition?
• How do I delete a recording entirely if a DTMF sequence is detected using norecord-dtmf?
• How do I suppress recording based on SIP headers using norecord-header?
• What is the difference between pauserecordingdtmf and norecord-dtmf?
• How do I enable packet deduplication for multiple sensors or interfaces?
• How do I save audio files to a single folder using saveaudio_singlefolder?
• Why are RTP packets not associated with the correct call legs when SIP and RTP are on different NICs or VLANs?
• What is `auto_enable_use_blocks` and why is it required for deduplication?
• What is the difference between `deduplicate_ipheader = yes`, `ip_only`, and `no`?
• How do I configure deduplication when packets arrive from different network paths with different TTL values?
• How do I decrypt TLS-encrypted SIP traffic?
• How do I capture and filter SIP PUBLISH, INFO, UPDATE, or other non-call SIP methods in the GUI?
• What is `save_sip_history = requests` and when should I use it?
• How do I make SIP PUBLISH packets searchable in the GUI "SIP requests" filter?
• How do I configure IPFIX to receive RTP QoS from Oracle SBC?
• How do I set up SIPREC recording?
• How do I enable Whisper audio transcription?
• How do I configure Kamailio siptrace mirroring?
• How do I set up Ribbon SBC monitoring profile mirroring?
• How do I use the traffic dumper to capture specific traffic?
• How do I enable CDR summary for faster dashboard queries?
• What is cdr_summary_interval and how does it affect aggregation?
• What is rtp_check_both_sides_by_sdp and when should I use it?
• How do I configure energy level detection for audio analysis?
• How do I configure VoIPmonitor to capture and save video RTP packets from WebRTC calls using VP8, VP9, or H.264 codecs?
• What is savertp_video and how does it differ from savertp?
• How do I enable video RTP packet saving in VoIPmonitor?
• Why are video RTP streams not being saved or captured in my PCAP files?
• What is cdr_country_code and how does it affect country flags in CDR view?
• Why are country flags not showing in the CDR view even though GeoIP is enabled?
• How do I configure VoIPmonitor to display country flags for caller and called numbers?
• What happens if I set cdr_country_code = no in voipmonitor.conf?
• How do I capture custom SIP headers like Referred-By or Diversion in the CDR?
• What is the custom_headers directive and how do I use it?
• How do I configure custom SIP headers for filtering and reporting in the CDR?
• How do I enable DTMF, silence, or clipping detection?
• What is SSRC in RTP and why does VoIPmonitor drop packets with zero SSRC by default?
• How do I fix missing audio or dropped RTP packets during silence periods?
• How do I capture RTP packets with zero SSRC from VoIP gateways or PBX systems?
• What does allow-zerossrc do and when should I enable it in voipmonitor.conf?
• Why are my calls showing missing audio during silence periods and how do I fix it?
• What is t2_boost and when should I use it?
• How do I fix CPU bottlenecks where a single defrag thread runs at 100%?
• What does the error "packetbuffer: MEMORY IS FULL" mean and how do I resolve it?
• How can t2_boost help with high traffic threading bottlenecks?
• How do I monitor VoIP traffic from a Windows host when port mirroring is not available?
• What is scanpcapdir and how do I use it for offline pcap processing?
• How do I configure VoIPmonitor to process pcap files from a directory instead of live capture?
• How can I use tcpdump and scanpcapdir to monitor traffic from Windows without SPAN port?
• Which configuration options were removed in sniffer version 2025.09.1?
• What deprecated options should I remove from voipmonitor.conf when upgrading?
• What are the modern replacements for vxlan, packet_buffer_total_size, and udp_reassembly?
• What options should I remove when upgrading to sensor version 2025.09.1?
• Are vxlan, vxlan_port, and vxlan_skipcrc still supported in the latest sniffer?
• What should I use instead of the deprecated sipdefrag and defragment_max_size options?
• How do I replace deprecated max_sip_size and interface_snaplen options?
• What deprecated SIP processing options are no longer needed in version 2025.09.1?