Tunnel SSH via jumphost
Nowadays many companies use a so-called jumphosts for access to their servers. While this makes it easier for the network admins and (if configured properly) more secure, it adds an additional hop for all the users interested in using the servers behind the jumphost.
So if a programmer wants to reach his dev server the following will happen:
programmer@workstation:~$ ssh jumphost programmer@jumphost:~$ ssh devserver programmer@devserver:~$ [...]
Combined with some command line switches to ssh that might be necessary to connect this is a quite tiresome exercise. In order to make life easier for the programmer the following can be added to the .ssh/config on workstation:
Host devserver ProxyCommand ssh jumphost nc -w5 %h %p
If you (like me) want to use your local ssh agent and the jumphost (actually
jmp.yourcompany.com) has ssh running on the non-standard port 12345
(security by obscurity) a complete example could look like this:
Host jumphost ForwardAgent yes HostName jmp.yourcompany.com Port 12345 Host devserver ProxyCommand ssh jumphost nc -w5 %h %p
Your routine to connect to the devserver would go from
programmer@workstation:~$ ssh -A -p 12345 jmp.yourcompany.com programmer@jumphost:~$ ssh devserver programmer@devserver:~$ [...]
to
programmer@workstation:~$ ssh devserver programmer@devserver:~$ [...]