DHCP problem in OS X

[tpjg]

could be proxy arp

I have run into this very same problem. Sometimes the Mac would get an IP address just fine, other times it would complain that the IP was already in use. The same thing can happen on (RedHat) Linux machines.

In my case the definitive solution was in disabling proxy arp on the (Cisco) router for the interface where I was connecting. Before accepting the OFFERed IP it seems my Mac would send out an ARP to verify that the IP that was offered was really available and then the router would reply that the IP was taken by one of it's (Vlan) interfaces.

Regards

PS if you're connecting directly using Ethernet to an ISP I wish you good luck trying to reach the right people and explaining the above

 

[Alessio.Aguirre]

I had this problem where I suddenly could not get a DHCP address. Same network, but suddenly could not get an IP. Different machines could get an IP, 1 mac could not.

This is what I did that worked.

1. Delete wireless service from "Automatic" location
2. Turn off all firewalls
3. Add Wireless service back
4. Re-enable firewall

I think something got corrupted somewhere and it just had to be rebuilt.

You are the wind beneath my wings.