[c-nsp] Decnet, LAT, MOP ... anybody?!?

[Brian McMahon]

On Apr 6, 2006, at 12:32, Netfortius wrote:

> Thank you for your reply. This is the challenge - I mentioned LAT  
> and MOP as I
> know they are not routable, but I cannot tell if the traffic I am  
> seeing is
> in real need for bridging or if I see it because it is bridged  
> (does it make
> sense? - this is the only way I could describe my problem).

If the traffic is originating on one side of the bridge, and you're  
seeing it on the other, then that is due to one of three things:

(1) The traffic is unicasted to a MAC address on your side, therefore  
"needs to be bridged".

(2) The traffic is broad- or multicasted, which needs to be bridged  
only if something on your side really cares (is, for example,  
listening to service advertisements).

(3) Your bridge is unicast flooding, which is a completely separate  
problem.

> For example - I am seeing conversation between an interface of one  
> VAX on one
> LAN (that weird MAC address which is specific to DEC), and the  
> Ethernet
> interface of the Cisco router - which, if it was to be routing -  
> would have
> been indicative of need to cross the boundaries, but which - being  
> that it is
> identifying by tethereal as LAT, makes me wonder if it is not in  
> fact just
> some broadcast reaching the router, but with no need to traverse it.

What's the destination MAC address of those LAT messages?  LAT does  
broadcast services, IIRC.

> Also - as all the VAXes on either side are supposed to boot locally  
> (MOP
> part), I am wondering if the traffic I see being MOP related is not  
> - in
> fact - visible just because I am bridging, not that it really needs  
> to cross
> LANs ...

At some point, you're probably going to have to break down and figure  
out what services your old boxen are really depending on.  "Just turn  
off bridging and see what breaks" is risky, because there may be  
"things that break" that you won't detect for quite a while (MOP  
booting, f'rinstance).

For example:  Do your VAXen really boot off MOP?  If so, what do they  
boot from?

-- 
Brian McMahon <brian dot mcmahon at cabrillo dot edu>
Computer Networking and System Administration Instructor
Cabrillo College, Aptos, California



-- 
Brian McMahon <brian dot mcmahon at cabrillo dot edu>
Computer Networking and System Administration Instructor
Cabrillo College, Aptos, California