Where do you configure the tcp ip stack on mac os x?
The Mac OS X TCP/IP stack is derived from the FreeBSD stack but
configuring TCP/IP stacks is more of a Windows thing than a Mac OS
X thing. Depending on just what you want to achieve/what the
problem is... trashing the SystemConfiguration's preferences.plist
(but keeping a copy for reference purposes is probably a good idea
;-), or simply switching from a wireless connection to an Ethernet
connection (or vice versa), and restarting will rebuild the
settings.