wan network routing

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From - Thu Aug  3 14:50:45 2000
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Newsgroups: comp.unix.sco.misc
From: bill@wjv.com.REMOVEME (Bill Vermillion)
Subject: Re: Network Design questions
Organization: W.J.Vermillion - Orlando / Winter Park FL
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In article <8ma73r$3h0$1@slb6.atl.mindspring.net>, David H. Funte <none> wrote:

>I have two Openserver 5.04 servers in two different cities.

>They are connected via PPP over a low bandwitch 38k connection. My
>goal is to keep trafic between cites at a minimun - while allowing
>full access to each server, and all print servers on the network.

>I am planning to do the following..

>(1) Connect both servers with subnet mask of 255.255.0.0
>
>            Server #1 IP is 192.168.1.1   - GATEWAY
>            Server #2 IP is 192.168.2.1   - GATEWAY

With a 192.168.1.1 and 2.1 you only need a 255.255.252.0.  If you
had chosen 192.168.0.1 and 192.168.1.1 you could used 255.255.254.0
The former supernets four 256 address blocks while the latter only
two.    

.........
>-------------------------------------------------------

>I've tested this, and it seems to work. However I have these
>questions.
>
>The servers are part of the 255.255.0.0 subnet mask, and the PC's
>in each town are part of the 255.255.255.0 subnet mask which form
>the local network. Since each server is the Windows gateway, any
>requests for the other cities addresses are routed through the
>local gateway to the other city - since the two servers are part
>of the same netmask. However any traffic that is part of the local
>network stays local.

>Question #1: Is there anything *BAD* about mixing netmasks.

You don't 'mix' subnets.  You use them to split of combine groups
of addresses into more manageable or routeable hunks.

>Question #2: does this setup actually acomplish my goal of minimizing
>traffic over the 38k PPP connection?

Not really.  But you mention internet connection below - and didn't
mention here - which router has the internet connection. That make
a difference in how the routing tables should be set up.

>---------------------

>Question #3: Each city has it's own internet router. The address of
>each router is 192.168.1.201 in City #1, and 192.168.2.201 in City
>#2.

>        I've noticed that I can list the UNIX server as the only
>gateway on both LANs if I add the following to the UNIX routing
>table.

>        City #1 UNIX routing table:  route add 0.0.0.0  192.168.1.201
>        City #2 UNIX routing table:  route add 0.0.0.0  192.168.2.201

You only use the 0.0.0.0 for what is sometimes called the gateway
of last resort.  I'm assuming only one router is connected to the
internet and the other goes through the first.  If so only the
non-connected can have 0.0.0.0 routed to the connected one, but
make sure the connected one has a route to the non-connected one
and with a netmask of 255.255.255.0.   That will make sure that
data only goes to where it is needed and will cut down on your
traffic - which was your stated design goal.

>        this seems to cause any "foreign" ip addresses to filter
>through to the internet gateway. The tracert command seems to prove
>this true.

I'd suggest reading up a bit on IP routing.  The 0.0.0.0 is used
only when previous routing statements don't match.  It is the 'use
this because I don't know where to got for this' and it sends it
out to the next router upstream.


>Is there anything wrong with creating a route to the 0.0.0.0
>network? It looks weird to me, but it seems to works.

No - it is needed if you have outside connectivity.  If you only
connect to each city you can dispense with that and make specific
routes so that if someone types an IP number outside the range you 
would get a 'network unreachable' or similar message.


-- 
Bill Vermillion   bv @ wjv.com 

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