Why won't a MacBook Pro running Snow Leopard obtain an IP address (DHCP)?

"If you're running a Snow Leopard Server, you'll need to go to Server Preferences and disable the security firewall so that the computer can access the DHCP on the router. Once that happens, you'll be assigned the correct IP address.

This took me several days and hours to figure this out. It's so frustrating since I don't know if this security feature is overkill if you're behind a NAT router."

"Obvious answer: Have you confirmed that the ethernet port is configured to get IP address via DHCP?

If DHCP is already set for this network inteface, go to the ""advanced..."" window and click ""Renew DHCP Lease"". Does this help?

Ugly hack workaround: Delete the ethernet network interface (select it and click the ""-"" button at the bottom). Create a new ethernet network interface."

On my unibody MacBook Pro 17" running Snow Leopard, the DHCP problem turned out to be fixed by switching from WEP to WPA2 security on the WiFi network. I had no problem using it with WEP on an iPad, two iPhones, and another MacBook Pro (unibody 13"). In fact, both MBP's are running 10.6.8 so I'm still not sure why one worked and one didn't, but after switching to WPA2 everybody's happy!

I had the same issue after upgrading from Leopard to Snow Leopard. Upgrading SL from 10.6 to 10.6.1 resolved it for me, but YMMV

"My answer to this other question (for Wifi, but still applicable to your issue) will clear out your network preferences, which will be much easier than reinstalling the OS.

Problem with Macbook air automatically not acquiring free wifi network dns or router address

When I wrote that 10.6.2 wasn't out, but again reinstalling the 10.6.2 combo updater would be a great step to take before an OS reinstall."