ok a dual nic or triple, quad etc (i have a quad
is basically the chips for multiple cards, and a pci-bridge.
saves real-estate.
i've got some servers here with well over 6 pci cards (with onboard video/sound/ethernet too).
so for routing services boxes, yes its important to have these multi-nic cards.
Btw, if you were to setup both dsl and cable on your linux/freebsd NAT firewall/gateway box, you could do asymetrical load-balancing...