I would prefer he NEC does the register so there is on place to manage.

IP Phone -- router1 -- INTERNET - router2 -- SIP Server -- NEC Server

Also, I forgot to add that the NEC system uses port 5070 to register SIP phones instead of 5060 if that makes a difference.

Sorry, I will try to explain better. I am trying to use the SIP Server to do all NAT translations for my hosted PBX. All the IP phones will be remote behind firewalls. The PBX (172.16.2.10) will be at my office behind my firewall (98.x.x.x). I want to use the SIP Server to be the NAT server between ...

The IP phone will be behind NAT coming to the SIP Server.

SIP Server will be behind firewall with all ports needed forwarded.

1. Brekeke Product Name and Version: SIP Server 3.5.5.2 2. Java version:8 3. OS type and the version: Windows 10 4. UA (phone), gateway or other hardware/software involved: NEC SV8100 5. Your problem: I am new to this and I am trying to set up the SIP server to only be a NAT transversal server ...