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From: JNC@XX.LCS.MIT.EDU ("J. Noel Chiappa")
Newsgroups: mod.protocols.tcp-ip
Subject: Re: 4.3bsd/subnetting
Message-ID: <12214109227.9.JNC@XX.LCS.MIT.EDU>
Date: Wed, 11-Jun-86 23:05:52 EDT
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Posted: Wed Jun 11 23:05:52 1986
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	I don't think there's any easy way to do this if you can't make your
4.3 gateway accept more than one IP address for a single interface. I guess
you've considered the obvious brute-force solutions like putting N different
interfaces in your gateway machine, or getting another class B network and
making that the subnetted net.

	Being able to assign a single physical net several logical net numbers
makes renumbering things really painless; you don't have to have a massive
flag day. That's such a useful capability for a gateway to have that I'm
surprised 4.3 is missing it; are you sure there's no way to do it? Maybe
someone should or has added it to 4.3.
	Of course, the difficulty factor of doing this will really depend on
how the insides of the 4.3 IP layer are arranged. I can tell you from
experience in the C Gateway that some places you really have to work at it to
make things work with multiple addresses per interface. Consider sending out
routing packets (you can't use the all 1's broadcast address since people may
get routing packets intended for the other logical net), checking for incoming
broadcast packets, etc!

	Noel
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