Asterisk + Aastra 480i CT over NAT with dynamic IP

This one is a doozy.

I got my Aastra 480i CT connecting to a test Astrisk server here in the office. It wasn’t especially difficult.

Now to connect it to Asterisk running on our server outside the office.

Our office is on NAT. Internally we have 192.168.100 etc. And our NAT box’s public interface has a dynamic IP assigned by the ISP.

It looks like the thing to use would be STUN or Session Border Controller, but there are some problems. From what I can tell, the Aastra 480i CT doesn’t support STUN, and it looks like Astrisk doesn’t provide SBC support.

Any good solutions on this? I guess one thing I can do is run a VPN and tunnel the whole thing over there, so that neither the phone nor Asterisk is even aware of NAT happening. But that introduces yet another layer of complexity which I would prefer to avoid.

This whole thing is a bit complex to set up.

Thanks for any suggestions.

I realize this is an extreme necro-thread, but I thought I would follow up with how I did it:

It works great. I did need to use a PC to run as an OpenVPN bridge for this. Yes, it’s a bit complex but it really works! Sound quality is good.

Better alternative is to use snom phones which have built-in OpenVPN support. Once you figure it out it’s not hard to get it going.