[Simh] EXT : VAX/VMS 6.2 DECnet turned off, still resetting MAC address

[Hittner, David T (IS)]

It won’t hurt your SIMH VAX to have a published “Decnet-like” MAC address of aa-00-04-00-20-10, unless there is a MAC collision on the local LAN segment. It’s just a MAC address after all.
Any decnet protocol packets that are sent out will be ignored (dropped) by the local IP router as unroutable.
Any IP packets will route in/out to the currently set MAC address *unless* you’re trying to run this connection over wireless Ethernet which is a whole different story..
If you are having MAC collision problems, you can also change the “fake” decnet address to another “fake” decnet address which doesn’t collide.

If you want to get back to the “hard assigned” 08-00-2b-aa-bb-cc MAC address, you can deinstall the DECNET package from your installation, OR stop decnet from running on system startup (to stop the decnet setup packet) .

You can also fix this by modifying the system parameters with an interactive boot and write, but I forget the details.

Dave

From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Bill Deegan
Sent: Tuesday, October 20, 2015 4:31 PM
To: simh at trailing-edge.com
Subject: EXT :[Simh] VAX/VMS 6.2 DECnet turned off, still resetting MAC address

Greetings,
I'm migrating a VMS 6.2 system from real hardware to simh VAX.
We're running on EC2 so DECnet's a no go.
We've disabled the DECnet startup on the system, but when I turn on tracing I see:
DBG(42740138541)+> XQ ETH: writing  dst: 02:41:0C:98:92:09  src: AA:00:04:00:20:10  proto: 0x0800  len: 98  crc: B5981F43
Is there a way to enable the debugging before booting up the VAX?
Barring that is there a way to prevent simh catching the "setup packet" and changing the SRC MAC address?
-Bill
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