Hi! Kamailio does not forward the received 503 response but instead generates a new 500 response. Failure routes are not activated. U 2010/04/14 15:08:26.201865 83.136.22.111:5060 -> 83.136.32.159:5060 SIP/2.0 503 Service Unavailable Via: SIP/2.0/UDP 83.136.32.159;branch=z9hG4bK2a5a.0d5ea987.0;received=83.136.32.159 Via: SIP/2.0/UDP 10.10.0.51:5086;received=83.136.33.3;rport=5086;branch=z9hG4bK2901533893 From: <sip:klaus.darilion@labs.nic.at>;tag=1939498352 To: <sip:01888801505641636@labs.nic.at>;tag=as1b74528e Call-ID: 3387977514 CSeq: 21 INVITE Server: Asterisk PBX 1.6.2.6 Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO Supported: replaces, timer Content-Length: 0 X-Asterisk-HangupCause: Unallocated (unassigned) number X-Asterisk-HangupCauseCode: 1 U 2010/04/14 15:08:26.201865 83.136.32.159:5060 -> 83.136.22.111:5060 ACK sip:01888801505641636@labs.nic.at SIP/2.0 Via: SIP/2.0/UDP 83.136.32.159;branch=z9hG4bK2a5a.0d5ea987.0 From: <sip:klaus.darilion@labs.nic.at>;tag=1939498352 To: <sip:01888801505641636@labs.nic.at>;tag=as1b74528e Call-ID: 3387977514 CSeq: 21 ACK Max-Forwards: 69 Content-Length: 0 # U 2010/04/14 15:08:26.201865 83.136.32.159:5060 -> 83.136.33.3:5086 SIP/2.0 500 Service Unavailable Via: SIP/2.0/UDP 10.10.0.51:5086;rport=5086;branch=z9hG4bK2901533893;received=83.136.33.3 From: <sip:klaus.darilion@labs.nic.at>;tag=1939498352 To: <sip:01888801505641636@labs.nic.at>;tag=c3829fdbb3bfc7416671e56cae8e633d-a9b5 Call-ID: 3387977514 CSeq: 21 INVITE X-Info: (83.136.32.159:1035) Enforcing NAT traversal for local caller X-Info: (83.136.32.159:1035) Enforcing symmetric response routing Server: kamailio (3.0.1 (i386/linux)) Content-Length: 0 Is this a feature or a bug? thanks klaus