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New Member

SoftPhone over VPN audio issue

Having a "one-way" audio issue when IPC connects over VPN to any Main Office IP Phones (7960). Remote IPC (softphone) shows "0 Received" Packets, but the IP Phone shows them as being sent.

This does NOT happen if IPC contacts another IPC on a PC at Main Site, or any kind of phone at the other branch offices.

Have looked at all of the audio settings on the VPN IPC unit, they are correct.

Any ideas?

  • Other Collaboration Voice and Video Subjects

Re: SoftPhone over VPN audio issue

Ensure that both Endpoint can ping each other.

Try also sniffing the Call (with Ethereal) to see where the problem is.

New Member

Re: SoftPhone over VPN audio issue

Ping / traceroute from both ends without a problem. I have started to run ethereal to capture packets while reprlicating the problem. Unfortunately, I amat a loss as to what I am looking for in the dumps. Any guidance would be appreciated.


Re: SoftPhone over VPN audio issue

Look at the time before RTP Packets (if any) were sent.

Sniff both Call were no problem was encountered and the the one with one Way voice and compare them, its not the easy way but you will understand more things on whats happening with your voice packets.

See also if your Firewall is blocking anything.

Check also this link:

New Member

Re: SoftPhone over VPN audio issue

I will give it a try and post results. Thanks for taking the time, I really appreciate your assistance.

New Member

Re: SoftPhone over VPN audio issue

Try to sniff the Ethernet traffic during call setup at the CallManager. When Callmanager sends Call Control messages to remote party, it could send wrong IP address or UDP port as an RTP parameters.

Another components could block the traffic are firewalls. How do you have your VPN tunnel built? Do you use Cisco VPN Client? What terminates your VPN traffic at the central location? PIX, VPN3000 or Router? Traffic may go one way without a change, and some protocol FixUp may be triggered for this traffic on the way back. If you have access to firewall logs, check if you have any traffic dropped.

Good luck,