Is it possible to have a request for an IP rerouted back into the server it came from?

The reason I ask is that we have a server sitting on the same LAN as our live servers and won't to make sure they can't talk to each other. I am well aware there are better ways to do this, but this is how it is.

Is it possible to setup so that any request for an IP could be routed back to say, localhost, or some erronous network address?

Thanks

I think it is possible to accomplish that task using some software like iptables or ipfilter.
Unfortunately I haven't the knowledge for suggesting a configuration, and I think that the right tool to use also depends on the platform you're using.