Question : Problem: Mac Pro not getting DHCP address

 I have a Mac Pro that absolutely will NOT grab an address from DHCP. At first i thought it was the prorgam called Little Snitch, but i uninstalled that and no dice. Safe mode, no dice. It has dual gigabit NIC's, neither one will grab an address from any port we hook to it. Ive tested the cables and the ports with a Fluke and they check out fine. Mac book pro grabs addresses fine on the same ports. The Mac OSX firewall are all set to "allow all connections".
  Now the frustrating part is that i put in a static address and still no network communication. Ive tried DHCP with manual address..nothing. Bootp...nothing. Turned the NICS on and off, nothing. Even removed one an re added it from the network config screen..nothing. This is highly frustrating and the user really needs to get back online. any thoughts or ideas would be greatly appreciated.

Answer : Problem: Mac Pro not getting DHCP address

I've run into that before.  Everything looked right, packets seemed to be received, but couldn't pick up DHCP even though everything seemed to be configured correctly.  What had happened is the two NICs had been aggregated together, and they had lost their connection to the Xserv.  Check to see if the nics are bonded, if so, try breaking the bond and renewing the lease.  If your situation is like mine, that should fix it quickly.