Hmmmm. Well then you probably don't want to use Linux/BSD as a router, as a substantial amount of DIY is required for anything beyond relatively simple routing. MPLS support (on Linux) for example is in early phases and requires integrating separate pieces and is best supported on Fedora9. Needless to say, Fedora isn't designed for reliable/stable operation and long term deployment.
I have yet to look into *BSD based solutions, but hear very good things about firewall performance. I don't know about BGP/OSPF/MPLS etc support on FreeBSD but am going to wager a guess its on par with Linux if not better.
The underlying OS is responsible for packet forwarding, but none of them do any significant routing protocols natively. Adding on a package such as Quagga or OpenBGPD is required for that, and the results of each should be relatively similar across platforms. The only major caveat is that Quagga OSPF is currently a disaster on FreeBSD 7. Don't try it. We added a server that was advertising some stuff, with multiple interfaces, using a config identical to what we do under FreeBSD 6. Not only did it randomly not work, but it also randomly killed OTHER OSPF speakers elsewhere in the network, including on non-directly attached networks in another OSPF area (we'd log in and see no neighbors). OpenOSPFD appears to be the fix for that. Simpler, smaller, but dumb enough that it advertised 127.0.0.1 into our OSPF environment when we were trying to get some aliases on lo0 advertised, which caused freaking out of pretty much every OSPF-speaking UNIX server we have (sigh). BGP is straightforward, except for things like MD5, which can be a bit dicey. Quagga is very good, and much less expensive than, something like Cisco for a route server, from what I've heard over the years. You'll notice some of the Route-views boxes are Quagga or Zebra (its predecessor). ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.