[Asterisk-Users] How to register a SIP phone on Asterisk behind NAT

[Zeeshan]

Hi everybody,

One of my client's Asterisk box is behind NAT. They have only one public
IP on which they have their router. I can access the Asterisk server
using port forwarding (port 22) for SSH. Now this client wants to
connect two SIP phones to this Asterisk box from two remote locations.
How can this be done. If I forward ports, e.g. 5060-5070 to this
Asterisk box, there is no guarantee that the SIP phones will be using
the same ports from the remote locations, because ports get changed over
the Internet, like for another scenario with my client on public IP,
remote SIP ports are 17355, 61949, 61666 etc., though they are
configured 5060 on the phones, and 5060 in sip.conf.

What is the solution in this scenario of registering SIP on Asterisk
behind NAT?

Thanks,

Zeeshan A Zakaria