Hi all, I have a problem with routing BYE messages (when called UAC sends BYE) when connection between two Kamailio (1.5.1 with identical configurations) proxies is done by TLS/TCP. WORKING: UAC#1 <-- UDP/TCP/TLS --> Proxy#1 <--UDP--> Proxy#2 <-- UDP/TCP/TLS --> UAC#2 NOT WORKING: UAC#1 <-- UDP/TCP/TLS --> Proxy#1 <-- TCP or TLS --> Proxy#2 <-- UDP/TCP/TLS --> UAC#2 By looking at ngrep log I found out that when “UAC#1” sends INVITE, “Proxy#1” sends right “Contact” header (Contact:<sip:bob@IP_ADDRESS_OF_UAC#1:6126;transport=udp>) to “Proxy#2” , but “Proxy#2” sends wrong “Contact” header (Contact:<sip:bob@IP_ADDRESS_OF_PROXY#1:39879;transport=udp>) to “UAC#2”. When UAC#2 sends BYE, it is sends message with this wrong header and when it arrives on “Proxy#1” proxy doesn’t sends BYE message to UAC#1. Or when UACs with TCP, this are “Proxy#1” errors: DBG:core:tcp_send: no open tcp connection found, opening new one ERROR:core:tcp_blocking_connect: poll error: flags 18 ERROR:core:tcp_blocking_connect: failed to retrieve SO_ERROR (111) Connection refused ERROR:core:tcpconn_connect: tcp_blocking_connect failed ERROR:core:tcp_send: connect failed ERROR:tm:msg_send: tcp_send failed ERROR:tm:t_forward_nonack: sending request failed DBG:tm:t_relay_to: t_forward_nonack returned error What bothers me is that when I call the other UAC, he can hangup the call (even when he is CALLED UAC), then I restart both proxies and it is other way around. I do not know if I described problem clearly but I am lost in where to look next so any help would be appreciated. Why proxy change Contact header when I switch from UDP to TCP between proxies? I'm not rewriting Contact header and only thing that I change in configuration when switching from UDP to TCP is this: if($rd=="example.com") { t_relay("tcp: example.com:5063"); exit; }