robespierre wrote:
as long as you choose a sysid that is a valid unicast MAC address, the onboard ethernet should work with any address you want. the reason for keeping the same address is for software licensing, and to avoid confusing routers/switches that have the station MAC address stored, for VLAN assignment, proxy ARP, etc.
If you have the proper MAC address go ahead and use it. That way you don't have to worry about keeping records of your MAC allocations (and you don't have to worry about taking your box to a different network where everyone has their dead Sun programmed with C0:FF:EE), and you get to keep the Sun MAC prefix so the machine comes up on NMAP et al as a Sun rather than whatever (because the other way of ensuring a "good MAC" across different unknown networks is to get a cheapo PC-type card, retire it, and use the MAC on your Sun - but then it comes up as "Netgear" or whatever...)
Note that you need to program two numbers for everything to be good: the MAC and the system serial number. On Suns they're different. SSN's big use is licensing.