So sometimes you need to access some isolated system from remote but the only way to talk to the system is through another system to which you only have ssh access on one port.
It turns out that this isn't a problem at all since the only thing you require to access a foreign system through an intermediary system is ssh.
The following one liner allows just this:
ssh -N -L LOCAL_PORT:target.domain.tld:TARGET_PORT USER_NAME@proxy.server.host.tld
no commandflag. It means that no command should be executed uppon connection. This has as a side effect that You will not get a normal shell after connection. Instead the ssh process will block the terminal until it times out or you exit with
CTRL + c.
[bind_address:]local_port:target_host:target_portin short this means that the port
local_portwill be routed to
As always much more in depth information can be had via
man ssh so go there in case You want to learn the inner workings of ssh.