Hi,

We're running a system with Kamailio running in front of Asterisk just handling registrations and forwarding everything else to Asterisk. But we're having an issue during hangup on incoming calls. If the initiator hangs up, the call completes successfully. But if one of our phones hangs up, the BYE message comes back with a 404 "Not Found" and the call doesn't hang up on the carrier side.

According to the carrier, it's because the IP in the contact on our ACK message goes to their audio IP while the header of our BYE points to their signaling IP. 

ACK sip:[Kamailio Pub IP]:5060;line=sr--rkpsDAp6YAp6DIpZDZmZeI2ZYI26YIRVDcpsDIpsem* SIP/2.0
Via: SIP/2.0/UDP [Carrier Signaling IP];branch=z9hG4bK2236.1402e7b4.2
Via: SIP/2.0/UDP [Carrier Audio IP];received=[Carrier Audio IP];branch=z9hG4bK07a8bccb;rport=5060
Route: <sip:[Kamailio Pub IP];r2=on;lr=on;ftag=as67cef00d;nat=yes>,<sip:10.120.0.1;line=sr--rkpsDthVDIhVDNh6Ogo6eKh6eAQs4LRflC2srQRflC2srGqAl-CAP6rZrZkGDmpGed2APtCvlx1>
From: "+16014477389" <sip:6014477389@[Carrier Audio IP]>;tag=as67cef00d
To: <sip:6016025063@[Carrier Signaling IP]>;tag=as643b40ca
Contact: <sip:6014477389@[Carrier Audio IP]>
Call-ID: 4aaefec90826a2a221f0af9500ad211b@[Carrier Audio IP]
CSeq: 102 ACK
User-Agent: packetrino
Max-Forwards: 69
Content-Length: 0