Hi, I'm having the following scenario UA <---> Prox1 <----> Proxy2 <-----> B2BUA <------> UA Proxy2 and B2BUA are connected on LAN and Proxy1 is adding his own Contact Alias and Proxy 2 is adding his own Contact Alias I'm adding Alias via using the following function set_contact_alias("1") as it will remove other contact alias but is causing the problem in the case of BYE coming from B2BUA. Is there is a way to find if the contact alias is already set? How I can replace the local IP alias with domain name when request is coming from B2BUA and alias is added by Proxy2. Here are logs to show problem in 200 sent by B2BUA and proxy2 add alias 10.44.44.2~6000~1 Now in ACK it is causing the problem SIP/2.0 200 OK Via: SIP/2.0/UDP sip.prox1.example.com:5060 ;rport=5060;received=3.18.1.21;branch=z9hG4bK2d66.a89039bedfe3d1113132f04c94b8a757.0 Via: SIP/2.0/UDP 192.168.1.168:50279 ;received=109.8.2.1;rport=45607;branch=z9hG4bKPj84875d08eafc48bfa6c29de5fe245cea Record-Route: <sip:sip.proxy2.example;lr;did=e84.87e2;rtp=bridge> Record-Route: <sip:sip.prox1.example.com;lr;did=e84.7452;rtp=bridge> From: "8001" <sip:8001@sip.example.com>;tag=0b9915abae654e21845fd4d7f577ede9 To: <sip:2501@sip.example.com>;tag=as1f4f6b1c Call-ID: a0095b9868924b0681225a8884a06c22 CSeq: 3687 INVITE Server: Voip Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE Supported: replaces, timer Session-Expires: 1800;refresher=uas Contact: <sip:2501@10.44.44.2:6000;alias=10.44.44.2~6000~1> Content-Type: application/sdp Require: timer Content-Length: 281 Ack for 200 ACK sip:2501@10.44.44.2:6000 SIP/2.0 Via: SIP/2.0/UDP sip.proxy2.example.com:5060 ;branch=z9hG4bK2d66.3c10a3b45e5c8caacbc5853d5e6418b2.0 Via: SIP/2.0/UDP sip.proxy1.example.com:5060;rport=5060;received= 3.18.1.21 ;branch=z9hG4bK2d66.788312006d5f7aedc058435cd203fed3.0 Via: SIP/2.0/UDP 192.168.1.168:50279;received= 109.8.2.1 ;rport=45607;branch=z9hG4bKPjf003c3bfe4ba423e9a0dedd647511dd3 Max-Forwards: 68 From: "8001" <sip:8001@sip.example.com>;tag=0b9915abae654e21845fd4d7f577ede9 To: <sip:2501@sip.example.com>;tag=as1f4f6b1c Call-ID: a0095b9868924b0681225a8884a06c22 CSeq: 3687 ACK Content-Length: 0 Thanks in advance