When developing for several customers, I have to circumvent a lot of issues around networking. The thing that most annoys me is when the SVN server is inaccessible from the server (for whatever reason).
Since I'm always working with tight deadlines, I don't have time to waste asking access on those routes, so I normally make use of the great SSH tunnel feature.
I assume that you are working on LAMP here and, therefore, won't explain how to do it on a Windows machine/server.
So, from your favorite terminal just type: