Inbound SIP-TRUNK no takes remote port from IPv4 header

Hi all,

I have a Distro FreePBX with public IP, connected directly to Internet. I've created a SIP-TRUNK with inbound registration. In other office I have other Asterisk behind a NAT.

The inbound registration works fine, but the problem is SIP-OPTIONS and other SIP communication, why? Because Distro PBX takes remote port of Contact header. That port is the standard 5060, but this is NOT the port which the remote router listens... that port can be random port, because the router of the other side does NAT.

Is possible to configure that Distro FreePBX takes the remote port from IPv4 header IP? This is the way to register endpoints, in fact, I also have hardphone is the other side and DistroFreePBX takes the port from IPv4 header IP, NOT from Contact header.

Thanks,