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VPN and softphones



We terminate road warriors to PIX 515e and have softphones installed on their machines. They are able to talk to phones behind the PIX (phones ring and voice goes both ways), but when two roadwarriors dial each other, the phones ring but there is no sound in EITHER direction. Can you help in suggesting a fix or giving debugging techniques? Thanks

1 Reply 1



I'm not a huge expert on this - however I don't believe that what you are trying to do will work with the VPN clients terminating on PIX. The PIX will not let you route packets that are VPN tunnelled traffic in and out of the same PIX interface - in this case your outside interface.

In order for you two softphones to talk to each other - they need to open up a direct RTP connection between themselves for the voice path. PIX will not allow this communication to happen as above. The call ringing is handled by a TCP connection with Call Manager which will work - hence the phones ring, but no voice.

I've just tested your scenario in one of our client's networks - and get the same symptoms. Softphone to LAN phone is fine - however softphone to softphone doesn't work - phones ring, but no voice. As above, I believe that this is a design limitation of the PIX.

The way around it would be to use a VPN 3000 concentrator as the VPN termination point rather than the PIX.

Hope this helps - probably not the answer you were looking for. I'm putting a VPN 3000 into our client's network as above shortly, so will let you know how I get on.

Barry Hesk

Networking Manager

Notability Solutions plc

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