[asterisk-users] 2 firewalls, different INVITES

[Robert Moskowitz]

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?


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