# tcpdump -nqt -s 0 -A -vvv -i eth0 port 5060 tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes IP (tos 0x10, ttl 64, id 7841, offset 0, flags [DF], proto UDP (17), length 32) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0a96 -> 0x3070!] UDP, length 4 E.. ..@.@......n.......).. ..... IP (tos 0x10, ttl 64, id 56244, offset 0, flags [DF], proto UDP (17), length 32) 162.249.6.110.sip > 94.197.121.154.62788: [bad udp cksum 0x81e4 -> 0x7506!] UDP, length 4 E.. ..@.@..A...n^.y....D........ IP (tos 0x0, ttl 49, id 57210, offset 0, flags [DF], proto UDP (17), length 882) 94.197.121.154.62788 > 162.249.6.110.sip: [udp sum ok] UDP, length 854 E..r.z@.1..9^.y....n.D...^..INVITE sip:+447479189410@domain.com;transport=udp SIP/2.0 Via: SIP/2.0/UDP 10.121.239.28:33940;rport;branch=z9hG4bK34177 Max-Forwards: 70 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Contact: Expires: 3600 User-Agent: domain/1.6.1/ONE A2003 Content-Length: 375 Content-Type: application/sdp v=0 o=user 0 0 IN IP4 10.121.239.28 s=Session SIP/SDP c=IN IP4 10.121.239.28 t=0 0 a=ice-ufrag:fcpie a=ice-pwd:5jmr7tq9hg8p1bksamspm6ui4i m=audio 21000 RTP/AVP 201 101 a=rtpmap:201 OPUS/48000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=candidate:1 1 udp 2130706431 10.121.239.28 21000 typ host a=candidate:1 2 udp 2130706430 10.121.239.28 21001 typ host IP (tos 0x10, ttl 64, id 56245, offset 0, flags [DF], proto UDP (17), length 375) 162.249.6.110.sip > 94.197.121.154.62788: [bad udp cksum 0x833b -> 0x0f49!] UDP, length 347 E..w..@.@......n^.y....D.c.;SIP/2.0 100 Giving a try Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Server: OpenSIPS (2.1.1 (x86_64/linux)) Content-Length: 0 IP (tos 0x10, ttl 64, id 7842, offset 0, flags [DF], proto UDP (17), length 1033) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0e7f -> 0x8e53!] UDP, length 1005 ....n.......)....INVITE sip:+447479189410@10.45.155.206:49148;transport=udp SIP/2.0 Record-Route: Via: SIP/2.0/UDP 162.249.6.110:5060;branch=z9hG4bK7432.36a62733.0 Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 Max-Forwards: 69 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Contact: Expires: 3600 User-Agent: domain/1.6.1/ONE A2003 Content-Length: 375 Content-Type: application/sdp v=0 o=user 0 0 IN IP4 10.121.239.28 s=Session SIP/SDP c=IN IP4 10.121.239.28 t=0 0 a=ice-ufrag:fcpie a=ice-pwd:5jmr7tq9hg8p1bksamspm6ui4i m=audio 21000 RTP/AVP 201 101 a=rtpmap:201 OPUS/48000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=candidate:1 1 udp 2130706431 10.121.239.28 21000 typ host a=candidate:1 2 udp 2130706430 10.121.239.28 21001 typ host IP (tos 0x10, ttl 64, id 7843, offset 0, flags [DF], proto UDP (17), length 1033) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0e7f -> 0x8e53!] UDP, length 1005 ....n.......)....INVITE sip:+447479189410@10.45.155.206:49148;transport=udp SIP/2.0 Record-Route: Via: SIP/2.0/UDP 162.249.6.110:5060;branch=z9hG4bK7432.36a62733.0 Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 Max-Forwards: 69 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Contact: Expires: 3600 User-Agent: domain/1.6.1/ONE A2003 Content-Length: 375 Content-Type: application/sdp v=0 o=user 0 0 IN IP4 10.121.239.28 s=Session SIP/SDP c=IN IP4 10.121.239.28 t=0 0 a=ice-ufrag:fcpie a=ice-pwd:5jmr7tq9hg8p1bksamspm6ui4i m=audio 21000 RTP/AVP 201 101 a=rtpmap:201 OPUS/48000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=candidate:1 1 udp 2130706431 10.121.239.28 21000 typ host a=candidate:1 2 udp 2130706430 10.121.239.28 21001 typ host IP (tos 0x10, ttl 64, id 7844, offset 0, flags [DF], proto UDP (17), length 1033) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0e7f -> 0x8e53!] UDP, length 1005 ....n.......)....INVITE sip:+447479189410@10.45.155.206:49148;transport=udp SIP/2.0 Record-Route: Via: SIP/2.0/UDP 162.249.6.110:5060;branch=z9hG4bK7432.36a62733.0 Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 Max-Forwards: 69 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Contact: Expires: 3600 User-Agent: domain/1.6.1/ONE A2003 Content-Length: 375 Content-Type: application/sdp v=0 o=user 0 0 IN IP4 10.121.239.28 s=Session SIP/SDP c=IN IP4 10.121.239.28 t=0 0 a=ice-ufrag:fcpie a=ice-pwd:5jmr7tq9hg8p1bksamspm6ui4i m=audio 21000 RTP/AVP 201 101 a=rtpmap:201 OPUS/48000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=candidate:1 1 udp 2130706431 10.121.239.28 21000 typ host a=candidate:1 2 udp 2130706430 10.121.239.28 21001 typ host IP (tos 0x10, ttl 64, id 7845, offset 0, flags [DF], proto UDP (17), length 1033) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0e7f -> 0x8e53!] UDP, length 1005 ....n.......)....INVITE sip:+447479189410@10.45.155.206:49148;transport=udp SIP/2.0 Record-Route: Via: SIP/2.0/UDP 162.249.6.110:5060;branch=z9hG4bK7432.36a62733.0 Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 Max-Forwards: 69 To: From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Contact: Expires: 3600 User-Agent: domain/1.6.1/ONE A2003 Content-Length: 375 Content-Type: application/sdp v=0 o=user 0 0 IN IP4 10.121.239.28 s=Session SIP/SDP c=IN IP4 10.121.239.28 t=0 0 a=ice-ufrag:fcpie a=ice-pwd:5jmr7tq9hg8p1bksamspm6ui4i m=audio 21000 RTP/AVP 201 101 a=rtpmap:201 OPUS/48000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=candidate:1 1 udp 2130706431 10.121.239.28 21000 typ host a=candidate:1 2 udp 2130706430 10.121.239.28 21001 typ host IP (tos 0x10, ttl 64, id 7846, offset 0, flags [DF], proto UDP (17), length 32) 162.249.6.110.sip > 188.29.164.243.45353: [bad udp cksum 0x0a96 -> 0x3070!] UDP, length 4 E.. ..@.@......n.......).. ..... IP (tos 0x10, ttl 64, id 56246, offset 0, flags [DF], proto UDP (17), length 420) 162.249.6.110.sip > 94.197.121.154.62788: [bad udp cksum 0x8368 -> 0xe180!] UDP, length 392 E.....@.@......n^.y....D...hSIP/2.0 408 Request Timeout Via: SIP/2.0/UDP 10.121.239.28:33940;received=94.197.121.154;rport=62788;branch=z9hG4bK34177 To: ;tag=364660755d8ca6c0205a1abd0319a354-02a7 From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 INVITE Server: OpenSIPS (2.1.1 (x86_64/linux)) Content-Length: 0 IP (tos 0x0, ttl 49, id 57211, offset 0, flags [DF], proto UDP (17), length 431) 94.197.121.154.62788 > 162.249.6.110.sip: [udp sum ok] UDP, length 403 E....{@.1...^.y....n.D......ACK sip:+447479189410@domain.com;transport=udp SIP/2.0 Via: SIP/2.0/UDP 10.121.239.28:33940;rport;branch=z9hG4bK34177 Max-Forwards: 70 To: ;tag=364660755d8ca6c0205a1abd0319a354-02a7 From: ;tag=z9hG4bK66305466 Call-ID: 720153239504@10.121.239.28 CSeq: 1 ACK User-Agent: domain/1.6.1/ONE A2003 Content-Length: 0