MOP vs. Cisco, was Re: [HECnet] _PROVISIONAL_ map of HECnet, courtesy largely of Brian H.

[Dave McGuire]

On 01/09/2013 01:57 PM, Johnny Billquist wrote:
...and like this from NCP under VMS:

NCP> connect node gw physical address <MAC address> via
<circuit-name>

Note that the MAC address must have its octets delimited by
colons under Linux, and hyphens under VMS.

NCP>connect node gw physical address AA-00-04-00-01-F4 via ISA-0
Console connected (press CTRL/D when finished)


User Access Verification

Username: NCP>

Uhhh...HOLY CRAP!   That works from outside my network?!   Is it
working because you specified the circuit which gave it a path, or
because it gleaned the DECnet area/node address from the
(changed-by-DECnet) MAC address?   I'm guessing the latter.
(Peter?)

It works on any LAN, including across bridges, so the various
Internet based bridges we have make this work over some distance.
The communication is via MOP remote console packets, which are not
routed (just like LAT).   The addressing is direct to the MAC address,
whatever that happens to be at the destination.   If the node you want
to talk to supports MAC address aliases, the original address might
work, but in any case the DECnet style Ethernet address will work.

    That was my belief before five minutes ago, when Brian was messing
with me and got me all excited.   I was certain that MOP was an
unroutable, LAN-only protocol like LAT.   But then, apparently folks have
been booting DECservers via HECnet..?

Nothing strange with that. The bridge makes it appear as if you are on
the same ethernet segment.

  That makes sense...This will only work over bridged links, though.   My
Cisco GRE link (for example, in my configuration) should not propagate
that traffic. (and if it does, is anyone else seeing my LAT service
announcements? ;))

  If (say) Brian and I were to create bridge-groups in our IOS configs
that bridge across our Ethernet segments and the tunnel interfaces, that
should work.   I'm not too interested in doing that (it'd be lots of
traffic) but I'd expect it to work.

                                -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA