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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: An INTERESTING problem
Message-ID: <1991Jan10.194655.19685@Think.COM>
Date: 10 Jan 91 19:46:55 GMT
References: <9101100248.AA01030@desktalk.desktalk.com>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 22

In article <9101100248.AA01030@desktalk.desktalk.com> rlg@desktalk.com (Richard L. Gralnik) writes:
>The standard wisdom/procedure is to assign a subnet number to each remote
>office, another subnet number to each serial line, and another (or many)
>to the central site net.  We want to use an 8-bit subnet mask for the 
>obvious reasons, but the cost of this is that the serial lines become 2-node 
>subnets, thereby wasting 251 addresses (including 0 and 255) each.  Since 
>there are 20 remote sites, and the user wants redundant serial lines because 
>the network is mission-critical, we eat up 60+ subnet numbers right off the
>bat.  

Some routers (e.g. cisco) support configurations where the ends of a
point-to-point link are not assigned unique addresses, so the serial lines
don't have to be assigned subnet numbers.  As far as all the other hosts
are concerned, the two routers connected by the serial line are a single
virtual host (the serial link would be a slow virtual bus).  The routers
themselves need to know the number of at least one subnet connected to the
router at the other end of the link.
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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