Tony Graziano said, "They are supposed to be the same. The phone does not matter here. Sipxbridge manages that. Your vyaTta router is not doing symmetric nat."
Ok, I see that now. I traced the packets on the public side and indeed the firewall is rewriting the port number. So if I can change my firewall to symmetric NAT it will work. However, if I understand correctly, it will not be optimal. Please allow me to explain. First there is a problem with when the port is opened. Sipx request media be sent to port 30000 (for example) AND sipx will send media from port 30000. If the gateway send media to sipx before sipx sends media to the gateway the port will not be opened. Sipx must send media to the gateway first to allow the NAT masquerade rule to be established, thereby establishing an inbound connection. This has been verified with a packet trace. The gateway sends the ring tone to the phone upon receiving the INVITE, but the RTP stream is blocked. After the phone receives the 183 Session Progress it begins sending some media (also a ring tone???). This opens the port and allows the gateway's ringtone through, which is then heard on the phone handset. At least that's how it would work if I had symmetric NAT. The second problem is that sipx doesn't need to be involved in the media. Ideally sipx would leave the SDP alone so that the gateway would send media directly to the phone. This is possible if the firewall performs the ALG function by opening the port within the SDP and creating a DNAT rule to forward the traffic to the phone. This would allow my network solution to be much more scalable. Working is better than not working, so of course if I can't implement the optimal solution what you said is fine. Please correct me if I misunderstood something. Thanks again, Brian _______________________________________________ sipx-users mailing list sipx-users@list.sipfoundry.org List Archive: http://list.sipfoundry.org/archive/sipx-users Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users sipXecs IP PBX -- http://www.sipfoundry.org/
