I have a SIP trunk to Broadvoice. My Asterisk box (1.4.13) is on public addresses behind a firewall. Originally it was behind a Linksys WRT54G running sveasoft. Sveasoft really can't NOT do NAT even when you turn it off. My Asterisk box is defined as the DMZ box to Sveasoft and it seemed like it was leaving all packets alone. Now I switch to a Centos-based firewall configured with Shorewall (which only compiles Netfilter commands then steps out of Netfilter's way). There is NO hint of NATing on the Shorewall firewall. Calls from Boradvoice to my Asterisk box worked just fine with the Sveasoft firewall but fail with the Shorewall. And the problem is in the INVITE where in the first case there is and SDP to use a different address (than Broadvoice's SIP server) for the RTP flow, but that is not in the INVITE with the Shorewall firewall. I have attached Wireshark traces of the 2 INVITEs. What am I missing that is causing this behaviour? -------------- next part -------------- A non-text attachment was scrubbed... Name: Itfails Type: application/octet-stream Size: 745 bytes Desc: not available Url : http://lists.digium.com/pipermail/asterisk-users/attachments/20080104/4b69b924/attachment.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: itworks Type: application/octet-stream Size: 744 bytes Desc: not available Url : http://lists.digium.com/pipermail/asterisk-users/attachments/20080104/4b69b924/attachment-0001.obj