How to set up end-to-end NAT and socket forwarding?

Question

linux

Situation: The
PBX server with Asterisk is connected to the internal network, access to the Internet from which is only through Proxy.
This same Proxy does not pass SIP packets, most likely on port 5060.
Task:
Connect to a SIP server, which, of course, is on the Internet, for ENUM calls. It's not about the quality of communication, the main thing is to get through.
Idea:
Somewhere on the Internet, set up a server that will listen on TCP/UDP port 80 (since the proxy will most likely miss such packets) and redirect to the IP address and port of the desired SIP server. And from our PBX, connect exactly to the IP of this special host, and to port 80.
At the moment, a host with Centos 7 with an external address is already ready.
https://www.centos.org/docs/4/html/rhel-sg-en-4/s1...
Here is the thematic documentation, but somehow nothing works yet).

Answer 1

Do a normal nat with port group forwarding. As far as I remember, the proxy does not know how to push ports back.
Or vpn to a host with nat / direct ip that can turn traffic to the asterisk, but these are lags and crooked crutches.

Answer 2

The easiest way to do this is through SSH port forwarding:
ssh [email protected] -o "ProxyCommand=nc -X connect -x proxyhost:80 %h %p" -L:10000:SIP-server:5060
After that, specify the server address localhost:10000 to Asterisk . Also, if the firewall does not release on ports other than 80 and 443, then it makes sense to raise the remote SSH server on port 80 or 443.