IP Masq/network card support


Out of curiosity, does OS X do IPv4 packet forwarding (also known as ip masquerading or network address translation)? I know it could given the right utils, but does it come with the equivalent of linux ipchains? Also, does anybody know if oddball hardware does/will work (even if unsupported)? Ex: I have an intel 82557 100bt ethernet card...drivers are available for this under linux, I doubt they're available currently under OS X, but does OS X support any style of loadable modules/drivers? I imagine I could rewrite the driver to work, just so long as there's a way to actually load it...
Thinking about moving from linux to osx, just need those answers :).