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New Member

Can't route VoIP traffic over VPN


I wonder if anyone could give me some light regarding the following

In one site I have a 2811 and in the other site I have a 2811 with a PIX506E.

Both routers are running CallManager Express with IOS versions:



The site to site VPN is up and working. I can do a

ping source

and get 4 replies back.

Also, I can place any calls, from any of the two branches ok. It is only when I try to phone an extension number of the other branch that I have problems (i.e. 2106). The phone rings, and even recognises who I am phoning on the other branch but when the other person picks up the phone I can't hear them and they can't hear me.

I have set the dial-peer to send the traffic accross the VPN on both routers. ie.:

dial-peer voice 10010 voip

destination-pattern 21..

session target ipv4:

dtmf-relay h245-alphanumeric

codec g711alaw

Thank you for any help


Re: Can't route VoIP traffic over VPN

Let me understand what you try to say here:

1. you can call from branch to main site, you hear each other both end, right??

2. you can call from branch to branch, but no audio at all, right??

If yes... then you see the url i give you, that might cause your problem. PIX version 7.0 improves support for spoke-to-spoke VPN communications as it provides the ability for encrypted traffic to enter and leave the same interface.

Please see the following website:



Please rate the helpful post.

New Member

Re: Can't route VoIP traffic over VPN

There are only two branches.....

Let's say Manchester and London

I can phone from either branch to the main (outside) number of that branch.

i.e. from London I can phone Manchester on 01618348243......

However, I can not phone Manchester directly using an extension number

i.e. From London, I want to phone Peter Smith in Manchester using his extension 2106 (this is the extension of Peter in Manchester)

When I phone Peter's extension, his phone in Manchester ring's 4 or 5 times, my phone in London recognises that I am phoning Peter in Manchester and it displays Peter's name on the screen, the phone icon even changes to off-hook when Peter picks up the phone......however, he can't hear me and I can't hear him

The topology is as follows:

London Router --> Manchester PIX --> Manchester router

Please notice:

from Manchester's router I can ping London's FA interface doing ping

However, from London's router, I can't ping Manchester router FA interface

unless I do ping source

Both Manchester and London are running CallManager Express

It seems to me that the routers are able to establish the connection using skinny but then the IP phones are not able to communicate/send over the RTP traffic and that's why we can't hear each other??

Again, thank you for any help

Hall of Fame Super Gold

Re: Can't route VoIP traffic over VPN

You may have a problem in the policy map on the PIX (london), so RTP is not sent in.

You have an H.323 hop and the router will source and terminate all RTP traffic between sites.

Only phones registered to the same CCME will send RTP directly between themselves, unless mtp is configured in ephone.