The MAC address will be assigned based on the HOSTID.

Sun Fire[TM] 6800 only

MAC addresses on the 6800 are fixed. Thus changing the 6800 from a single segment to a dual segment will not change the MAC assignment.

Domain      MAC Address     HOSTID
  A     08:00:20:d8:8c:38  80d88c38
  B     08:00:20:d8:8c:39  80d88c39
  C     08:00:20:d8:8c:3a  80d88c3a
  D     08:00:20:d8:8c:3b  80d88c3b            

Sun Fire[TM] 4800, 4810 & 3800 only

For the other three platforms, Sun Fire 4800, 4810 and 3800, the ID has two MAC addresses for the domains. The first MAC address will always be used for Domain A. The platform will assign the second address to Domain B or Domain C, depending upon how you segment the platform. It is never possible to use Domain D with these three platforms. In addition, you can never have both Domain B and Domain C running.

Single Segment Dual Segment

Domain     MAC Address      HOSTID       Domain     MAC Address      HOSTID
  A     08:00:20:d8:8c:38  80d88c38        A     08:00:20:d8:8c:38  80d88c38
  B     08:00:20:d8:8c:39  80d88c39        B     ff:ff:ff:ff:ff:ff  ffffffff
  C     ff:ff:ff:ff:ff:ff  ffffffff        C     08:00:20:d8:8c:39  80d88c39
  D     ff:ff:ff:ff:ff:ff  ffffffff        D     ff:ff:ff:ff:ff:ff  ffffffff