[SR-Users] Kamailio under NAT

Hello, I am trying to start kamailio+rtpengine+asterisk in docker with docker-compose (not in network host mode). And I faced behavior that I can't understand. When my phone(fanvil) sends a register to kamailio with his ip in contact - 192.168.88.55 (to host's ip address 192.168.88.55), kamailio 200OK answers with "received=172.18.0.1" param in Via. (172.18.0.1 it is host's docker interface, kamailio's ip is 172.18.0.4) After that my phone unregisters with Expires: 0 and sends a new register with 172.18.0.1 in contact. Is that correct? Is there any way to fix this? 2020/06/05 12:05:51.764617 172.18.0.1:46142 -> 172.18.0.4:5060 REGISTER sip:192.168.88.55 SIP/2.0 Via: SIP/2.0/UDP 192.168.88.100:5756;branch=z9hG4bK14305253915361123;rport From: akamvm <sip:1000@192.168.88.55:5060>;tag=1125027099 To: akamvm <sip:1000@192.168.88.55:5060> Call-ID: 2849918516212-27188555511609(a)192.168.88.100 CSeq: 1 REGISTER Contact: <sip:1000@192.168.88.100:5756> Max-Forwards: 70 Expires: 3600 Supported: path User-Agent: Fanvil X3S 2.10.2.6887 0c383e217eb9 Allow: INVITE, ACK, OPTIONS, BYE, CANCEL, REFER, NOTIFY, INFO, PRACK, UPDATE, MESSAGE Content-Length: 0 2020/06/05 12:05:51.765716 172.18.0.4:5060 -> 172.18.0.1:46142 SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.88.100:5756 ;branch=z9hG4bK14305253915361123;rport=46142;received=172.18.0.1 From: akamvm <sip:1000@192.168.88.55:5060>;tag=1125027099 To: akamvm <sip:1000@192.168.88.55:5060 Call-ID: 2849918516212-27188555511609(a)192.168.88.100 CSeq: 1 REGISTER Contact: <sip:1000@192.168.88.100:5756>;expires=3600 Server: kamailio (5.2.1 (x86_64/linux)) Content-Length: 0 2020/06/05 12:05:51.779447 172.18.0.1:46142 -> 172.18.0.4:5060 REGISTER sip:192.168.88.55 SIP/2.0 Via: SIP/2.0/UDP 192.168.88.100:5756;branch=z9hG4bK251317807114669601;rport From: akamvm <sip:1000@192.168.88.55:5060>;tag=1125027099 To: akamvm <sip:1000@192.168.88.55:5060> Call-ID: 2849918516212-27188555511609(a)192.168.88.100 CSeq: 2 REGISTER Contact: <sip:1000@192.168.88.100:5756> Max-Forwards: 70 Expires: 0 Supported: path User-Agent: Fanvil X3S 2.10.2.6887 0c383e217eb9 Allow: INVITE, ACK, OPTIONS, BYE, CANCEL, REFER, NOTIFY, INFO, PRACK, UPDATE, MESSAGE Content-Length: 0 2020/06/05 12:05:51.780479 172.18.0.4:5060 -> 172.18.0.1:46142 SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.88.100:5756 ;branch=z9hG4bK251317807114669601;rport=46142;received=172.18.0.1 From: akamvm <sip:1000@192.168.88.55:5060>;tag=1125027099 To: akamvm <sip:1000@192.168.88.55:5060 Call-ID: 2849918516212-27188555511609(a)192.168.88.100 CSeq: 2 REGISTER Server: kamailio (5.2.1 (x86_64/linux)) Content-Length: 0 And new register: 2020/06/05 12:05:51.780287 172.18.0.1:46142 -> 172.18.0.4:5060 REGISTER sip:192.168.88.55 SIP/2.0 Via: SIP/2.0/UDP 192.168.88.100:5756;branch=z9hG4bK2696168232620424454;rport From: akamvm <sip:1000@192.168.88.55:5060>;tag=2649930762 To: akamvm <sip:1000@192.168.88.55:5060> Call-ID: 257831362525663-2610472014851(a)172.18.0.1 CSeq: 1 REGISTER Contact: <sip:1000@172.18.0.1:46142> Max-Forwards: 70 Expires: 3600 Supported: path User-Agent: Fanvil X3S 2.10.2.6887 0c383e217eb9 Allow: INVITE, ACK, OPTIONS, BYE, CANCEL, REFER, NOTIFY, INFO, PRACK, UPDATE, MESSAGE Content-Length: 0 2020/06/05 12:05:51.781208 172.18.0.4:5060 -> 172.18.0.1:46142 SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.88.100:5756 ;branch=z9hG4bK2696168232620424454;rport=46142;received=172.18.0.1 From: akamvm <sip:1000@192.168.88.55:5060>;tag=2649930762 To: akamvm <sip:1000@192.168.88.55:5060 Call-ID: 257831362525663-2610472014851(a)172.18.0.1 CSeq: 1 REGISTER Contact: <sip:1000@172.18.0.1:46142>;expires=3600 Server: kamailio (5.2.1 (x86_64/linux)) Content-Length: 0 -- Aydar A. Kamalov