How to solve the problem with routing?

Question

Asterisk

The server has a virtual machine with SIP.
External IP <-> NAT -> 172.16.0.1 <-> XEN Virtual SIP Ubuntu 14.04 Asterisk 13.x
Routing is configured correctly. Everything works when we use the Softphone via the mobile network.
But when from one office, where the local addresses are also 172.16.xx, the interlocutor is heard, but the voice does not go away. As I understand it, he is trying to find this server inside the local network, which is located within the framework of another. How to solve this problem.
EX has Nat mode: Yes (force_rport, comemedia) Chan_sip

Answer 1

If the networks are the same 172.16.0.x, then it will not work.
It is necessary to change one of the networks to 172.16.1.x, for example, and prescribe routes