I am working with a partner to enable SIP between a local SIP server and 2 Polycom phones located across a WAN connection.

The server is located behind a Cicso ASA with SIP translation enabled, and the on the partner's side there is a Sonicwall NSA240 firewall, with 2 Polycom phones behind it.

We are receiving SIP traffic from the partner, but they are never receiving audio (RTP traffic). In the SIP/SDP packets, we specify the RTP port dynamically, and the media server sends audio, but it never reaches the phones.

Is there some setting that we might be missing that would enable the RTP traffic to be setup dynamically?

1 Answer 1


The "simple" answer is VPN, which obviates the need for cunning tricks. Otherwise you might look at STUN.. (need an external server) but wether going from behind NAT to behind NAT is a great idea... I am not convinced!

  • We had not looked into a stun server, I will have to look into that option.
    – chills42
    Feb 18, 2011 at 23:15

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