Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!sri-unix!sri-spam!ames!ucbcad!ucbvax!hi.UUCP!kurt From: kurt@hi.UUCP (Kurt Zeilenga) Newsgroups: comp.protocols.tcp-ip Subject: Re: How do you break up a B class number? Message-ID: <8707271742.AA26964@hi> Date: Mon, 27-Jul-87 13:42:49 EDT Article-I.D.: hi.8707271742.AA26964 Posted: Mon Jul 27 13:42:49 1987 Date-Received: Tue, 28-Jul-87 05:32:03 EDT Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 39 Brandon@isi.edu writes: > 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? The reasons why we would like to split the B into different-sized subnets is simple. Address space. Right now we are projecting to have over 1k hosts on our main ethernet (actually a combination of thin and fat wires connected together using repeaters and smart bridges, like DEC's LAN 100 bridge). We also have many subnet that are being installed. Some of which are very small. To accomadate the main cable we would have to use a mask like 0xfffff800. This means we have split our B into 32 subnets each of 2k hosts (minus all ones and all zeros, of course). Anyway, 32 subnets will probably not be enough. Most (if not all) of our subnets will be gatewayed directly to the main ethernet (so subnetting the subnet won't really come into the problem) > 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. We are not planning to do any hacking. Since there is no real software solution at this time (unless you hack), maybe a hardware solution is in order. Anyone know of where we could pick up a few "smart bridges" real cheap? > Bob Braden - Kurt (zeilenga@hc.dspo.gov)