High number of users and network

I want to run a load test with 3000 users but I am concerned about network clogging. I know some of you guys have run load test with more number of users than that. Can somebody point me how should I go about doing this? Only thing I can think right now is split the load on 3-4 machines and run it manually.

BTW, What I mean by network clogging is my 100mb lan connection clogging.

What happens exactly?
Do you saturate your NIC’s bandwidth?
Do you run out of file descriptors?

I have run test with 500 users (closed model). I was keeping a track of network activity, which was around 65%. NIC’s bandwidth is the concern right now.

I read some of the old posts. Looks like I can use jenkins to cluster instead of manually running the tasks. Will that be a right approach?