The passive recording method is achieved by connecting the recorder server to a monitor port of a switch (SPAN/RSPAN port). The monitor port receives all of the traffic for each trunk that need to be recorded. The recorder captures all the traffic, including the RTP media streams and the SIP/H.323 signaling messages. SIP/H.323 trunks usually connect the call control server with the PSTN gateways or establish a direct IP trunk connection with the service provider.

Using Verba Recording System, multiple recording servers can be deployed in order to support multi-site configurations or branch office networks and/or high volume systems with or without redundancy.

Advantages

There is no connection to the CUCM server(s), so there is no extra capacity requirement at all.
In case of CUCM failure, the recording system is not affected, the recording can work continuously even in SRST (Survivable Remote Site Telephony) mode (if a local recording server is deployed at the remote side).
Because of the passive approach, the flow of the call is not affected at all.
Can be easily deployed and maintained.
Using Verba multi-site deployment architecture, the system can be adapted very well to fit a wide array of use cases.
If high-volume traffic should be recorded, the system can be scaled easily.
Monitor port technology is widely used approach. In most cases it can be easily configured and used.
Silent monitoring can be supported natively by the recorder.
Mobile phones can be recorded if the calls are routed through a SIP/H.323 mobile adapter (makes sense for transferred or forwarded calls only).

Considerations

Encrypted calls cannot be recorded.
Internal calls between IP phones cannot be recorded.
Only SIP and H.323 trunks are supported by Verba. (MGCP is not supported)
Automatic announcement of the recording cannot be done by the recorder itself. An external IVR should be involved.
Directory number/extension information is usually not available.

Possible deployment of passive, trunk-side call recording:

Single Server solution: All Verba services (Administration, Recorder) are on one server.
For installation guide see: Installing a Verba Single Server solution
Media Repository + Recorder Server: The Verba administration/storage and the Recording server is deployed separately.
For the installation guide see: Installing a Verba Media Repository and Installing a Verba Recording Server

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