Hi, finally I found out, what makes dns failover selecting a different send socket compared to the failed branches' send socket (when force_socket is NOT set): http://lists.kamailio.org/pipermail/sr-dev/2013-January/017880.html For a consistent default behaviour (set send socket to received socket if no force socket set) I suggest to fix t_fwd.c as follows: Change line 1071 to : old_uac->request.dst.send_sock:msg->rcv.bind_address, Change line 1086 to: old_uac->request.dst.send_sock:msg->rcv.bind_address, Cheers Jasmin