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From: braden@ISI.EDU
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  How do you break up a B class number?
Message-ID: <8707271647.AA00575@braden.isi.edu>
Date: Mon, 27-Jul-87 12:47:59 EDT
Article-I.D.: braden.8707271647.AA00575
Posted: Mon Jul 27 12:47:59 1987
Date-Received: Tue, 28-Jul-87 04:49:02 EDT
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I'd like to understand the reason that you feel the need to split
a class B network into different-sized subnets.  What happens if
you stick to a single subnet size?  

Although some of the comments in reply to your message have been somewhat
overblown, the fact is that the technical mechanism to handle
different-sized subnets of the same network is not generally available
today.  It may require carrying a 32-bit subnet mask along with each IP
(sub-)network address in whatever IGP is used within the subnetted
network.  The only current IGP which does carry such a mask is Dave
Mills' Hello protocol used in the Fuzzballs; however, you could probably
hack the BSD routing table and daemon to do so.  If you are not in a
position to roll your own IGP in this fashion, you had better stick to a
single subnet mask.


Bob Braden