SSH through multiple hosts using ProxyCommand?

Solution 1:

Easy.

Assume the following network setup:

You should be able to use a ~/.ssh/config file that looks something like this:

host foo bar
    ProxyCommand ssh -x -a -q gateway.example.com nc %h 22

host baz
    ProxyCommand ssh -x -a -q foo nc %h 22

The idea here is that your SSH does know how to get to "foo", so an SSH there will succeed. And from there, you can "nc" to baz. And if there are other hosts on the internal private network alongside "baz", you can just add them to the "host baz" line.

This basically treats the host "foo" as the gateway to "baz", just as "gateway" is the gateway to "foo".

Clear?

Solution 2:

Regarding ghoti's answer: instead of using netcat ("ssh ... nc %h 22"), starting with OpenSSH 5.4, you can do this directly with: "ssh -W %h:22 ...". This way, you don't have to worry about whether netcat is installed in the right place.