Xref: utzoo comp.dcom.lans:1316 comp.protocols.tcp-ip:3393
Path: utzoo!mnetor!uunet!mcvax!enea!erix!per
From: per@erix.UUCP (Per Hedeland)
Newsgroups: comp.dcom.lans,comp.protocols.tcp-ip
Subject: Subnetting
Message-ID: <1607@erix.UUCP>
Date: 5 May 88 13:27:31 GMT
Reply-To: per@erix.ericsson.se (Per Hedeland)
Organization: Ericsson Telecom, Stockholm, Sweden
Lines: 46

Excuse me if the question below is trivial, but I really haven't seen much
discussion on subnetting, and neither RFC reading nor local asking-around
has gotten me very far...

This is the scenario: The basic structure of our LAN is a backbone segment,
to which a number of Sun server/client groups are connected. Each client group
has it's own Ether segment, with the server acting as gateway to the backbone.
Typically there are 5-10 clients in each group. There are currently some 20
such groups, but predictions are for hundreds in the not too distant future,
i.e. considering other connected equipment, far more than 256 addresses are
required for the backbone.

Due to us not being connected to the Internet, and inadequate planning of the
growth of the LAN, network numbering is a mess, which we would like to clean up
as soon as possible, and this prompts my question: It seems to be a terrible
waste of adress space to use a separate class C number for each of the client
groups, so we figured that subnetting would be appropriate, but how do we use
it to an advantage?

Specifically, given the abovementioned structure, there's a conflict between:

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.

and:

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

We do believe that the arguments for the current structure (such as handling
the load from diskless clients, avoiding extra cabling given the physical
location of servers and clients, allowing use of the backbone for e.g. DECnet
traffic) are valid, and it seems rather silly having to modify it to
accommodate the IP adressing scheme. But of course, neither the structure nor
the requirement for "automatic" routing are carved in stone, i.e. any and all
suggestions are welcome (preferrably via e-mail, and I will summarize to the
net if requested).

Thanks In Advance
--Per Hedeland

Internet: per@erix.ericsson.se
Non-MX:   per%erix.ericsson.se@uunet.uu.net
UUCP:     {mcvax,munnari,uunet}!enea!erix!per