Hello community!
We are about 110 to 170 users on a LAN who share a low bandwidth satellite connection. To optimize user experience, I have been assigned to making a web caching server. We have no need for filtering content. In our setup we have a have:

LAN with our clients - Router with user authentication - Satcom Router.

My thought was to make a transparent, bridged caching proxy between the satcom router and the user authentication router so the setup will end up looking like this:

LAN with our clients - Router with user authentication - caching proxy - Satcom Router.

The reason why I choose to use a transparent, bridged setup was to be able to plug the proxy in with no configurations required on routers and clients.
I have tried in 3 days to get a solution up and running with no luck. So now I ask you:

- What software would you recommend for this job?
- And do you have any other recommendations I will benefit from while working on this?

I am an IT professional who have worked with network and Linux before, but for some reason this project is giving me a hard time. This is the reason why I want to start from fresh, and hear you guys opinion on the matter.