At work, to do any manual inspection in the "backend" server for one of my projects I have to ssh into the "frontend" server first.

home~$: ssh -A paul@frontend
frontend~$: ssh backend
backend~$: |

This is only two layers deep, but it made me wonder how far people have had to go in their day-to-day work in order to work with their projects.

So, what's the deepest number of ssh tunnels you have gone up to? Why did you have to do it?