[HECnet] Same MAC address on different nodes

[Johnny Billquist]

On 2014-05-24 23:18, Hans Vlems wrote:
The DIX spec says that hardware addresses ( the ones you put in the simh configuration file starting with 08-00-2B) must be unique    .

Yes. But that is because no two controllers should have the same MAC address, because it would break communication on the ethernet. But what this really is about is the MAC address used during communication. And since the address is changed by DECnet, it that that address that needs to be unique from a technical point of view.

And it only actually needs to be unique within the same ethernet segment.

	Johnny


Verzonden vanaf mijn BlackBerry 10-smartphone.
    Origineel bericht
Van: Jean-Yves Bernier
Verzonden: zaterdag 24 mei 2014 23:14
Aan: hecnet at Update.UU.SE
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] Same MAC address on different nodes

At 10:21 PM +0200 24/5/14, Johnny Billquist wrote:

So "Physical" is not "Hardware", and there is no need to SET XQ MAC.
I tried and it maked no change.

Right. Since your machine will set a different MAC address anyway,
at start, when you enable DECnet. The physical address is whatever
you set in simh before starting. It have no actual relevance once
DECnet starts. If you were to run something else, which did not use
DECnet (such as Unix), the address you set in simh will be the
actual MAC address used, since IP do not change the MAC address of
interfaces. No need.


You mean "the Hardware address is whatever you set in simh before
starting". CEX will set it to "Physical address" (in DECNET parlance)
which is AA-00-04-00-(1024 x area + node).

The MAC address is AA-00-04-00-01-28 for DECNET and 08-00-2B-AA-BB-CC
for Linux.

So, a NIC may have different MAC addresses depending of the network
stack running. Am I right here?



Really hard to give a good explanation on why without having good
access to all parts of the setup to be able to test and examine
things.

Well, my system is working 99%, that's not so bad :)




-- 
Johnny Billquist                                   || "I'm on a bus
                                                                  ||   on a psychedelic trip
email: bqt at softjar.se                         ||   Reading murder books
pdp is alive!                                         ||   tryin' to stay hip" - B. Idol