How to add an SSH tunnel to an additional address on another server?

Question

linux

Greetings!
There is an ssh tunnel (A1)
There is a linux server (A2)
How to add an ssh tunnel to the A2 server in an additional address?
One could start with an ipip tunnel or pptp, or make a proxy from A1 and add it to A2. The whole catch is that nothing can be changed on the server from which we make the ssh tunnel (A1). Here they connected to it, made a tunnel and forgot.
Can I use a third server, to which somehow add all the tunnels by making vpn, and then do something on it and connect it to A2?
In short, I've been sitting dumb for a week now and I can't figure out what's what. I ask for advice and help. Thanks in advance :)

Answer 1

add a virtual network interface: linuxconfig.org/configuring-virtual-network-interf...
and then forward the desired remote port to the virtual interface and port you need:
ssh -L [bind_address:]port:host:hostport hostname (See https://www.freebsd.org/cgi/man.cgi?query=ssh&sekt...