Sniffing modes

Linux host

You can install or compile VoIPmonitor binary directly on linux PBX or SBC/SIP server. This does not requires additional hardware and changes in network topology. The only downside is that voipmonitor consumes hardware resources - RAM, CPU and I/O workload which can affect the whole system. If it is not acceptable to share hardware for voipmonitor the second common use case is doing port mirroring.

Hardware port mirroring

Port Mirroring is used on a network switch to send a copy of network packets seen on one switch port (or an entire VLAN) to a network monitoring connection on another switch port => voipmonitor dedicated linux box. Port mirroring on a Cisco Systems switch is generally referred to as Switched Port Analyzer (SPAN); some other vendors have other names for it, such as Roving Analysis Port (RAP) on 3Com switches or just port mirroring.

In case of hardware mirroring you often need to have additional ethernet port. Sniffer is configured to use this port (interface=eth1) and it automatically put the interface into Promiscuous mode. In case you need to mirror to more ethernet ports you can set interface=any in voipmonitor.conf which will enable mirroring on all interfaces but you need to set each ethernet interface into promiscuous mode manually

ifconfig eth1 promisc

Software packet mirroring

All in one

If the sensor is installed on the same server as MySQL and GUI you do not need to configure sensors in GUI. The GUI is reading PCAP files directly from local file system and database are connected via localhost mysql database.

Multiple remote sensors one DB/GUI server

Note: sensor = sniffer, sniffer = sensor

Sensors can be configured in two ways - mirroring all packets by the remote sensor to central sensor or the remote sensor is processing packets directly and only sends CDR to central sensor which is connected to the database (keeping pcap files on local storage located on remote sensors)

Standard remote sniffer

Remote sensor in standard mode processes all packets and stores CDR to database keeping pcap files on local disk. This setup generates minimal traffic between sensor and remote database (it sends only CDR)

Since version 20.0 there is new encrypted and compressed TCP protocol between sniffers. Here is minimal voipmonitor configuration which leaves all options to default (can be changed)

What you need to configure on remote sniffer:

edit file /etc/voipmonitor.conf

id_sensor = unique_number # must be < 65535
server_destination = serverip
server_destination_port = 60024 #can be any port server_password = somepassword

this example configuration will process packets and sends only CDR to the server.

Mirroring remote sniffer

If you want to mirror all packets (so the remote sniffer will not use much CPU and memory) include options showed above (server_destination and server_destination_port) and add one more option:

packetbuffer_sender = yes 

What you need to configure on server

edit file /etc/voipmonitor.conf

server_bind = 0.0.0.0 #this will listen on all IPs
server_bind_port = 60024
server_password = somepassword
#do not forget to configure mysql* options 

What you should see in GUI

The GUI will automatically add sensors in Main menu -> Settings -> Sensors The advantage of this new protocol is that remote sniffers can be used behind NAT - the GUI communicates with remote sniffers over the TCP protocol, the protocol is encrypted and compressed.

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