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New Member

H/W conferencing anomoly w/ NAT

Have a CM, 6506 w/ a 6608 blade (used for conferecing) and a AS5300 all with public IP addresses.

I have an IP phone at home using a 17xx router (IOS 12.1(5)T) with a dial-up connection to the internet - been using this for many months. IP phone is on private address (router using PAT or overload NAT)

Just added the 6608 and finding that when I attempt to conference on another party (either another IP phone or a PSTN call) my IP phone on the private address loses the receive voice path.

Everyone else can hear fine and they can hear me fine - I cannot hear anyone..

Thinking that the voice path from the 6608 blade is not being handled properly by the PAT.


Cisco Employee

Re: H/W conferencing anomoly w/ NAT

Sounds like a good guess to me.

Can you verify that you have connectivity between the 1750 and the 6608 conference port? Try to do a ping from the inside NAT network on the 1750 to the IP address assigned to the 6608 conference port. Also, look at a show port on the Cat6k and make sure that the conference port has the correct default gateway.

Another thing you can do if all this reveals nothing, is to perform a sniffer trace from a PC plugged into the back of the phone. Check to see if it is actually getting the RTP packets, and if so from what IP address and to what IP address. If you don't see any packets on this side, you may want to run the trace on the Cat side.