bandwidth monitor

Hello all, My company is looking at options to set up some of our older computers as routers. We would love to use SuSE Linux as the OS for those systems. We also need to monitor how much bandwidth each system on the network uses. Has anyone else done this and if so, what would you recommend for bandwidth monitoring? We've just downloaded SmoothWall and will check that out some time today... Thank you in advance for your help! Warm regards, Jordan Michaels