Bundle, phone line -> SPA3102 -> internet -> sip phone

Question

Asterisk

Good afternoon.
To be more specific, there is an Analog GSM Gateway ITS CGW- T/TS + Linksys SPA3102 VOIP Gateway in one country. In another country there is a regular sip phone (somewhat desirable). The question is how to set up this combination so that the connection works in two directions, incoming and outgoing calls?
When searching the Internet, I realized that theoretically it is possible to configure a bunch of pstn <-> spa3102 <-> internet <-> sip phone , but this is not a very optimal solution and it is desirable that spa3102 connects to some kind of server (asterisk?) on the one hand, but on the other hand, sip clients would connect to it and the result would be the following combination pstn <-> spa3102 <-> internet <-> voip server <-> internet <->
The question is, maybe someone has already tried a similar solution and can help with the configuration and / or advise which option to choose, with or without a server.
Thank you very much!

Answer 1

I set up SPA3102 to “forward” a telephone line via the Internet without additional servers from SPA2102 at the second end - everything worked. In principle, what will happen at the second end - the gateway or the phone should not matter. Calls are driven on the basis of dialplans, go in both directions. To work, both ends must have external IPs accessible to each other. Ideally, a VPN, because if you use external addresses without filtering at the firewall level, soon not only you will call through your gateway!

Answer 2

As an option, yes, we deploy the simplest server on *, we start several "internal" numbers on it, register the spa as one, and phones as the rest. But my advice is to set call directions specifically (otherwise, as esvaf says, soon half of Taiwan will call through this server), adjust iptables, etc.
Well, if suddenly something - please, than I can - I will help.