Chaining SSH Tunnels
So in an early post I described how to create an SSH tunnel. That is fine if you only need to connect to a server by going through a single bastion. In this post, I am going to provide an example for how to connect by going through multiple servers; in other words, how to chain SSH tunnels.
Suppose you want to connect to server E but in order to do so, you have to be on server D that you can only access from C which in turn can only be accessed from B that only A can access. The following should setup the necessary chain of SSH tunnels.
ssh -NL 6000:B:22 -o TCPKeepAlive=no -o ServerAliveInterval=15 A &
ssh -NL 6001:C:22 -o TCPKeepAlive=no -o ServerAliveInterval=15 localhost -p 6000 &
ssh -NL 6002:D:22 -o TCPKeepAlive=no -o ServerAliveInterval=15 localhost -p 6001 &
ssh -NL 6003:E:22 -o TCPKeepAlive=no -o ServerAliveInterval=15 localhost -p 6002 &
ssh localhost -p 6003
Welcome to E!
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