How fast does the dedicated network between the router and the PC running cflowd need to be?
Your first concern should be whether the router can handle the load fo running netflow itself. Unfortunately, trying it is the best way to find out, since everyone’s situation is different. Eveyone’s situation is different for the flow-export traffic load too. A general rule of thumb is to expect 30 (Ethernet MTU) packets per second per DS-3 or FDDI when using v5 flow-export. Expect more for an OC-3 (say 50 packets per second). A 10Mb/sec Ethernet should be fine in most situations unless you wind up putting a bunch of other stuff on it and it’s not switched. As for the machine running cflowd, it again depends on the load. CAIDA runs cflowd on a Pentium II 233MHz machines with 128Mb of RAM running FreeBSD. We haven’t had ethernet card issues, using old 3Com 509B(ISA), newer 3Com card (9xx), cards based on the DEC DC21x4x chipset (the DE500 card in particular), and Intel EtherExpress 10/100 cards (normally our preferred card). I don’t know that you’ll see any performance differences in F
