Re: Subnetting


Doug_Nelson@um.cc.umich.edu
Sat, 7 May 88 11:11:58 EDT


In message <In message <1607@erix.UUCP>, Per Hedeland writes:

> a) It appears that the intended use of subnetting assumes that all the "subs"
> of a "whole" net are interconnected, i.e. the backbone and the client
> segments in our case should be "subs" of the same "whole" - in particular,
> "automatic" routing by means of routed (which we desire) will not work
> otherwise, as far as I can understand.

Yes, that has to be true - you can only advertise your full network,
not your subnets, to the Internet at large.

> b) "Subs" of a given "whole" must be of equal size.

This is a mistaken assumption. There is nothing that prevents you
from using subnets of different sizes on a given net, except for
software that isn't up to speed on subnetting (notably SunOS 3.x).
For example, our campus-wide network is a class B sized subnet of a
class A network. The Merit network itself is a class A/2 subnet, and
Univ of Michigan has parceled out a number of class C-sized subnets.
I plan to pass out class C-sized subnets of our network (or possibly
smaller) to several other campus Ethernets, as soon as we get SunOS
4.0 installed.

Doug Nelson den@serv1.cl.msu.edu
Michigan State University 08071den@msu.bitnet
Computer Laboratory



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