We might be comparing Sun hw from different eras. The QFE cards I remember were in a very different address range from the onboard Ethernet (which was still 8:0

We might be comparing Sun hw from different eras. The QFE cards I remember were in a very different address range from the onboard Ethernet (which was still 8:0:20:... I think). Seems like the QFE MAC must have been in PRAM on the NIC then, at least. And I am pretty sure I remember the MAC address following the card, too. The problem I ran into was that when two same-MAC ports were connected to different segments/VLANs on the same layer 2 or 3 network device, that device wouldn't know what to do with the packets. Or it might send them down the wrong wire, which was a problem for me -- these were firewall boxes. :) Eventually Sun added a boot param (or a kernel config? Set from OBP or from a shell) that would automatically number the QFE interfaces sequentially on boot. That fixed the problem for me. Much later, they added the front-panel accessible smart cards that contained MAC, hostid, etc. I think that was the Netra series, intended for carrier grade RAIC installations.