How to let all traffic from a specific port into the l2tp tunnel on Mikrotik?

Question

Mikrotik

Good day!
I have the following task: I have a Mikrotik router, all traffic from its 80th port must be passed through a remote Privoxy proxy server, which is connected via an l2tp tunnel. The router successfully pings the proxy, successfully sends requests to it from the console.
Before the tunnel was created, the proxy server "just lay somewhere on the Internet" and the desired traffic was successfully wrapped by the following nat rule on the router:
/ip firewall nat add chain=dstnat action=dst-nat in-interface=bridge -local dst-port=80 protocol=tcp to-addresses=1.2.3.4 to-ports=8118
This rule does not work through a tunnel. I feel that the solution is somewhere nearby, but I could not find it yet.

Answer 1

You don't have a return route on the other side of the tunnel. To do this, you must either register a route, or enable masquerading in the tunnel:

/ip firewall nat add chain=srcnat out-interface=*tunnel_interface* action=masquerade