This says, "The IEEE ethernet standards state that the Media Access Code (mac) is assigned per node, and Sun writes its drivers per the standard. If your run 'ifconfig -a' as root, you will see that all NIC's have the same ethernet address."
You have to issue the following commands from the OBP before you boot the system
OK> setenv local-mac-address? true OK> reset-all
You could also make this change by issuing the following commands from the OS before rebooting.
#eeprom local-mac-address?=true #reboot
This will ensure that each NIC has a unique mac address as opposed to the default configuration where the mac address is selected from the IDPROM and is therefore the same for each NIC on the system which also means that the same machine can not have two NICs on the same subnet without making the above change.