[Simh] EXT : Unable to connect to ethernet

Hittner, David T (IS) david.hittner at ngc.com
Tue May 17 11:02:02 EDT 2011


If the standard XQ MAC of 08-00-2b-aa-bb-cc is used, and the virtual NIC is attached to a wireless controller, then any packets which are not addressed to/from your "registered" PC's wireless MAC address may be legally dropped out by the wireless router to conserve bandwidth.

The only way to debug a wireless router connection to run WireShark on the host PC and watch the packet traffic, while also running WireShark on a wired PC on the network to see if you see all the packets traversing the wireless link correctly. It almost never does what you think it will, because wireless routers are allowed to drop non-essential packets to conserve bandwidth, and non-TCP protocols tend to get axed, because home routers usually don't need to deal with non-TCP packets.

You can 'fake' the simulated NIC's MAC to be the same MAC as the PC's wireless NIC MAC to fool the wireless packet dropping, but this will only work if you are not running decnet phase IV or decnet phase V in compatibility mode, since decnet phase IV forcibly changes the hardware MAC to a decnet-encoded value. This technique will always work if you're only running TCP/IP on the simulated system, since the simulated NIC will see all the (matching MAC) IP packets, and throw out the incorrect IP-addressed packets. If you're running decnet phase V not in compatibility mode, this technique will still work, but decnet phase V will eject a lot of unknown protocol messages to the console - just set term opa0: /nobro/perm to shut it up, or use NCL to disable the warnings.

Some router/wireless card combinations will work flawlessly to route non-registered MAC addresses, most won't.

Wireless Ethernet "looks like" Ethernet .. but it isn't Ethernet.

Dave

-----Original Message-----
From: Robert F. Thomas [mailto:rft at asthomas.com] 
Sent: Tuesday, May 17, 2011 8:53 AM
To: Hittner, David T (IS); simh at trailing-edge.com
Subject: RE: EXT :[Simh] Unable to connect to ethernet

I thought that I had.  I did make many attempts.  The host system adapter's
MAC address was specified as the XQ0 MAC address, etc.

Sincerely,
Robert F. Thomas

 355 Providence Highway 
Westwood, MA USA 02090
(  Office Phone - (781) 329-9200
* mail to: rft at asthomas.com
 
-----Original Message-----
From: Hittner, David T (IS) [mailto:david.hittner at ngc.com] 
Sent: Monday, May 16, 2011 3:40 PM
To: Robert F. Thomas; simh at trailing-edge.com
Subject: RE: EXT :[Simh] Unable to connect to ethernet

You need to *carefully* read the SIMH FAQ section regarding wireless
Ethernet.

SIMH wireless networking is a lot harder to configure correctly than wired
Ethernet because it just "looks like" Ethernet, and because many wireless
routers suppress "unregistered" simulated MAC addresses to control
bandwidth.

Dave Hittner

-----Original Message-----
From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com]
On Behalf Of Robert F. Thomas
Sent: Monday, May 16, 2011 3:04 PM
To: simh at trailing-edge.com
Subject: EXT :[Simh] Unable to connect to ethernet

I omitted vax.inc:

set rq0 ra90
set rq1 cdrom
att rq0 vms.dsk
att rq1 vax071.iso
att xq0 eth1
set cpu 128M

Sincerely,
Robert F. Thomas

 355 Providence Highway 
Westwood, MA USA 02090
(  Office Phone - (781) 329-9200
* mail to: rft at asthomas.com
 


_______________________________________________
Simh mailing list
Simh at trailing-edge.com
http://mailman.trailing-edge.com/mailman/listinfo/simh



More information about the Simh mailing list