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From: markat@cyrano.llnl.gov (Mark Tassinari)
Newsgroups: comp.dcom.sys.cisco
Subject: subnet masks
Message-ID: <35985@boulder.Colorado.EDU>
Date: 13 Jun 91 18:33:53 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 29


We are in the process of converting a large (4000+ nodes) bridged network
to a more manageable (hopefully) subnet topology.  The network is divided up
into administrative domains that usually have just a single subnet, though 
there are several that have multiple subnets on a single cable.  We are making
use of Proxy ARP to ease the transition.

After these nets are moved to routers, it it worth going back to each host 
to change the subnet mask?  This can be a big job.  

I can see no compelling reason to go either way.  Changing the subnet mask is
the technically correct thing to do.  However, for those networks that have
multiple subnets on one cable, changing the subnet mask creates additional
traffic.  If two hosts that are on different subnets (but on the same cable,
and possibly sitting next to each other) need to communicate, each packet has
to go through the router. 

Have I missed something obvious?  I don't see a good reason to go and change
all those subnet masks.  What are the advantages of doing it 'right'?

Thx.

Mark


~~~~~~~~~~~~~
Mark Tassinari				markat@cyrano.llnl.gov
Lawrence Livermore National Lab		(415) 422-4090
PO Box 808   L-408			Livermore, CA 94550