ipcc silent monitoring

Unanswered Question
Nov 10th, 2008
User Badges:

Has anyone implemented silent monitoring with cat 3750s pre cm 6. Is there a restriction that the agent cannot be on a downstream switch from the voice monitor?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Aaron Harrison Tue, 11/11/2008 - 06:05
User Badges:
  • Super Bronze, 10000 points or more
  • Community Spotlight Award,

    Member's Choice, May 2015


There are two types of silent monitor setup with IPCC.

You can use Desktop Monitoring, whereby the CAD software sniffs the traffic and relays it back to the server. This has the following requirements:

1) PC must be able to see and read the dot1q encapped voice traffic - so 'Span to PC port' must be enabled on the phone properties in CCM, and the PC NIC must support dot1q. Most decent cards work OK.

2) Users must be using CAD.

The other type uses SPAN to get the packets from the edge ports to the server. This has one requirement:

1) The server must be able to see the voice streams in both directions being sent to, and from, the phone MAC address.

This means that you must SPAN the edge ports to the server if there are any L3 hops in the way (i.e. if you have a routed access layer, you can't span the gateways that are located on a different subnet to the phones and expect success).

I've succesfully had this working on lots of topologies - typically you need to RSPAN the edge ports back to the switch containing your CRS VOIP Monitor port.

You also need to be careful not to SPAN the same stream twice, or you get audio problems with playback (i.e. if you SPAN two edge ports both in and outbound, and the two ports call each other, you get distorted playback).



Please rate helpful posts...

whanson Thu, 11/13/2008 - 06:21
User Badges:


I am going to lay this out for you as you seem to have been through the wars. We recently took over support for customer not happy with current vendor. They use silent monitor but it is less than satisfactory. Supervisor listens on 3 particular phones and all is well. Other phones totally crappy. They are on the same switch, same phone load, same phone type, same switch. He did tell me something interesting that the 3 even if he doesn't monitor can still hear their conversations. Not sure I understand that at all. Any thoughts? He is using the rspan methodology even though they recently converted to cm 6

csanemeterio Fri, 05/29/2009 - 08:36
User Badges:

Excellent response !!

I am running the Cisco Supervisor Desktop in a win xp with SP2 in VMWARE (because my machine have SP3 and doesn't work), in the vmware machine ill see the supervisor desktop but the voice monitor icon its in grey (unavailable).

I checked the Span to PC port was ok in the agents phones.

Iam thinking perhaps my nic cards or the sharing card with vmware not support dot1q?

Any ways... if the problem is that, the option in the supervisor desktop is ok unavailable?

Best, Cristian


This Discussion