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New Member

Bad Interface in Media Negotiation. One way RTP.

I have a 3662 router that runs the 12.2.(1) Ios version.

The configuration is:

Cisco Gateway ---- Internet ----- SIP Phone


| Fa0/1

Voice Gateway ----- PSTN

| Fa0/0


Internal LAN

The Fa0/1's Interface of the voice gateway router is mapped with a global IP address. (No NAT).

All the UDP packets are authorized for the SIP Phone on the Access-List.

I generate a call from the SIP Phone to the Voice Gateway to exit on PSTN. The telephone is ringing but the router negotiates every time the Fa0/0 interface in the Media instead of the Fa0/1 (that received the Invite).

So I have a one-way RTP.

How the router negotiates the "speaking" Interface for the media?

PS: No default route is used.


New Member

Re: Bad Interface in Media Negotiation. One way RTP.

Voice gateway will choose the interface that's closest to the phone. In this case, since the phone is privately numbered on your internal LAN, that's why it's using Fa0/0 (which is, by the way, the phone's default gateway.) Privately numbered phones connecting to the Internet are ALWAYS a headache since they *HAVE* to have NAT of some sort so the inbound voice RTP stream can find it's way back in.

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