All the VAXen I’ve used or configured (including SIMH instances) have a hardware address like 08:00:2B:xx:yy:zz where the xx, yy and zz come from the label on the network interface or are assigned by me. I don’t have to work out MAC addresses that match the DECnet address since the software sets these when it initialises.
My SIMH ini files have
For Unibus e.g. VAX780 -
set xu enable
set xu type=DELUA
set xu mac=08-00-2B-11-07-80
attach xu eth0
For Qbus e.g. VAX3900 -
set xq enable
set xq mac=08-00-2B-11-06-50
attach xq eth0
Up to five SIMH instances run fine under Raspberry Pi OS bookworm 64-bit (aarch64) on a Pi3B+ that also runs pydecnet.
Tony