Internet address assignment

[Lap Yun Yau]

We just registered our Internet address and are now planning for
reorganizing of all networks within the company.  The following scheme
shows the relationship of nets and subnets:

        ====+====================+===============         Backbone Network
            |                    |
            |Dept A              |Dept B
        =+==+==+==+=        ==+==+==+==+==o==o===         Departmental Networks
         |  |  |  |           |  |  |  |                        (=o=   node)
         |  |  | =+====       |  |  | =+=====Net B.1      Dept Subnet 1
         |  | =+=====         |  | =+=====Net B.2         Dept Subnet 2
         | =+=====            | =+=====Net B.3            Dept Subnet 3
        =+=====              =+=====Net B.4               Dept Subnet 4

We want more than one backbone networks, with each backbone net connect
couple departments while each of these departments may have several
subnets.

How should I setup the subnet addresses?  Let's say we have a Class B
address, XX.YY., and we have two bytes (the third and the fourth octects)
to play with.

Method 1:

Backbones - XX.YY.30, XX.YY.32, ..., XX.YY.38
Dept Nets - XX.YY.40, XX.YY.60, ..., XX.YY.240
Dept Subnets - XX.YY.41, XX.YY.42, ..., XX.YY.49 for dept net XX.YY.40
             - XX.YY.61, XX.YY.62, ..., XX.YY.69 for dept net XX.YY.60
             - ...

Is this setup a true subnetting?  Our concerns are some software like
Interleaf using network license requires license server runs on, say, dept
B net and serves all subnets B.1, B.2, etc.  At present, we have only
backbone and dept nets hook to it and each net has it own class B address.
When Interleaf license server runs on, say, dept A's net, nodes in other
dept's net cannot run Interleaf.  Does anybody knows if the method 1
setting will work?

Method 2:

Let's play with the 3rd and 4th octects.
        3rd octect                              4th octect
+---+---+---+---+---+---+---+---+       +---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |       |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+       +---+---+---+---+---+---+---+---+
\      / \             / \                 / \                         /
backbone    dept nets         dept subnets             nodes

Then we can have 4 backbones, each backbone can have 16 dept nets, each
dept net can have 8 subnets, and each subnets can have 126 (128 minus all
0s and all 1s) nodes.  By looking at books and references on Internet
Addressing, it seems to us that it should work and really follow the
standard way for subnetting.  The subnet mask for every networks is
FFFFFF80.  Is it right?  Are we missing anything?  Can some network gurus
confirm that or give us some insight as to how to do it the right way?

If we follow this scheme, what should be the addresses for nodes like
routers, brideges, workstations, and computers attached directly to
backbone net, or dept nets.

================================================================= Super Backbone        |               |               |               |
        |               |               |       ========+======== Backbone 1
        |               |       ========+======================== Backbone 2
        |       ========+======================================== Backbone 3
==+==+==+==+==+==+==+==+==+==+==+==+==+==+==+==+================= Backbone 4
  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
  |  .  .  .  .  .  .  .  .  .  .  .  .  .  . =+============ Dept net 1
  |  .  .  .  .  .  .  .  .  .  .  .  .  .  .                ...
  |                                                          ...
=++==+===+===+===+===+===+===+============================== Dept net 16
 |   |   |   |   |   |   |   |
 |   .   .   .   .   .   . ==+=================== Subnet 1
 |   .   .   .   .   .   .                        ...
 |                                                ...
=+=============================================== Subnet 8

****************************************************************************

Many thanks.

uunet!smosjc!lapyun