You've given me lots to think about ! Thanks for all the input so far. A few queries for the replies if I may. My brain is whirring. Chris: You're right and I'm tempted. I've almost had my arm twisted to go down the proprietory route as I have some Cisco experience but have become pretty familiar with Quagga and tc. David: May I ask which NICs you use in the IBM boxes ? I see the Intels recommended by Mike have dual ports on one board (the docs say "Two complete Gigabit Ethernet connections in a single device • Lower latency due to one electrical load on the bus"). Patrick: That's what I was hoping to hear :) It's not the world's biggest network. Michael: Thanks very much. We have three upstreams. I guess 2GB of RAM would cover many more sessions. Eugeniu: That's very useful. The Intel dual port NICs mentioned aren't any good then I presume (please see my comment to David). Thanks again, Chris