With this trick we will learn how to use a multi-homed intermediate server as a gateway to access the internal network, all of this transparently to us.
It’s as simple as editing our config so that when connecting to hosts on the 10.10.30.0/24 network, it goes through SERVER, which obviously must have an interface on the LAN.
vi ~/.ssh/config
Host 10.10.30.*
ProxyJump SERVER
Now we can directly access the LAN hosts through SERVER using:
ssh 10.10.30.X