[Simh] Vax.exe emulator and Multinet network configuring

[Paul Koning]

> On May 9, 2019, at 7:55 PM, Johnny Billquist <bqt at softjar.se> wrote:
> 
> On 2019-05-10 01:46, Paul Koning wrote:
>>> On May 9, 2019, at 3:20 PM, Hittner, David T [US] (MS) <david.hittner at ngc.com> wrote:
>>> 
>>> (It's been a long time since I've played with SMAC on wireless. I did get it to work, but it wasn't worth the pain to me, so I upgraded to DECNET/OSI non-compatibility mode.)
>>> 
>>> IIRC, when you start DECNET IV, it sends a broadcast packet to see if there is an address collision with the hard-coded DECNET IV address before it changes the MAC to the DECNET IV MAC.
>> That's not in any DECnet standard.  It may be someone did that, and it wouldn't be a bad idea to do so.
>> BTW, some NICs allow enabling multiple individual addresses and choosing which one you want.  DEC made that standard fairly early on, once it became clear that combining LAT and DECnet on a single interface was a pain.  DEUNA doesn't do this, DEQNA does, and all the DEC single-chip Ethernet interfaces support it.  On such interfaces you'd use the aa-04 address for DECnet and the "hardware address" for other things.
> 
> Hum? My understanding is that the DEUNA and DELUA works exactly the same in this aspect. And combining DECnet and LAT is not a problem on of those interfaces, so now I'm curious what you are thinking of?
> 
> Also, at least under RSX, all software is definitely using the same MAC address for any and all network protocols you might be running, which includes DECnet, LAT, MOP, IP, ARP, and anything else you might want to throw at it.

That's certainly allowed, but as I said, most DEC NICs allow you to avoid the DECnet address for other protocols.

The difficulty was with VMS, which would start LAT before DECnet and use the hardware address for LAT if the individual address hadn't been overridden.  So your sessions would fail because the address would change.  The solution, with the DEUNA, was either to start LAT after DECnet, or to teach VMS the DECnet address via some other system parameter so it would be set at boot time, not wait until DECnet startup.  The multiple individual address feature was made a standard part of the DEC Ethernet architecture so you wouldn't need to do any of this; if a protocol needed a specific format address it could just use it, without bothering other protocols on the same machine.

	paul