IP Routing Question

[Monty J. Harder]

On Tue, 2 Jan 2001 08:28:12 -0600 mike neuliep <mike at illiana.net> writes:

> It is Cisco's accepted practice to take a network and subnet it 
> using a 30 bit
> mask.  This will leave you lots of networks with two usable host 

  I figured that part out, once I read that typical router software had
been upgraded to support "uneven" subnetting.  But that's still 4 IP
addresses used for every such link in every network in the world.  If I'm
right about this, there are a lot of "nominal subnets" out there that
don't need to be using up the address space at =all=.

> Your second question is a subnetting question.  Yes you can 
> advertise a route
> to a whole network to the rest of the world while behind the router 
> the network
> is subnetted.  This is actually preferred and most routers will 
> consolidate
> routing tables to keep routing table sizes down.  

  I understood that, too. It's half the reason for CIDR, after all.  (The
other half being conservation of address space by allowing more
granularity in forming net masks.)

  What -=NOBODY=- has answered yet, including you, is whether it's OK to
use "private" IP addresses for those subnets that link the routers
together, while keeping public IP behind them.  See all of those 10.x.y.x
and 10.x.y.y thingies in there?  =That= seems to be the $64K question. 
The instructor didn't have any specific reason why it wouldn't work, but
seemed to have a vague feeling that it must break some rule somewhere
because That's Not The Way It's Done.

  But TNTWID isn't good enough for Geeks Like Us, now is it?  Hell, no. 
We'd all be exclusively using MS and happy about it.  I always ask "If I
do this, what does it break?  Can we fix that protocol to make this
work?"  It seems to me like it =should= work, but I don't know enough yet
to know why it wouldn't.

> The biggest thing that scares me here is the quality of your 
> instructor! :-)
> But your employers have decided to subscribe to the Microsoft Money 

  Actually, the State of Kansas is paying for this, in the hopes that the
next job I get is one that pays so much better they'll get lotsa taxes
off me or something.  I have to come up with something quick, though.
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