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From: jason@hpcndjdz.CND.HP.COM (Jason Zions)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Network configuration problem
Message-ID: <810021@hpcndjdz.CND.HP.COM>
Date: 13 May 91 22:56:58 GMT
References: <75283@brunix.UUCP>
Organization: HP Colorado Networks Division
Lines: 51


   global internet
      |
      R
      |    net1
   ------------------------------------------
               |        |             |
               A        B             C
               |        |             |
   --------------  ------------  ------------
      net2           net3          net4


I don't know about your other routers, but HP 9000 Unix boxes do support
non-byte aligned netmasks; the HP internal network uses a netmask of
255.255.248.0 on a class A network.

Seems to me that you should configure all the nodes on net2 with a default
route through A's net2 address; similarly for net3 and B and net4 and C.
Each of the routers B C and R should have routes for the net2 network
through A's net1 address; similarly for B and net3, C and net4. Also, the A
B and C routers should use router R as their default route; this should give
everyone in your net visibility to the outside world as well.

The tricky (or ugly) part is what to do about the nodes on net1. You could
configure them with the specific routes for A/net2, B/net3 and C/net4 while
using R as the default router. Or, you could use just R as the default
router and depend on ICMP Redirect messages from R to install per-node
routes in the routing table on the net1 system. Finally, you could configure
the nodes on net1 to use proxy ARP (assuming all of A, B, C, and R support
it). Personally, I'd recommend the first configuration; it's a bot of a pain
to get all the systems on net1 configured, but the performance and network
impact are optimized.

Using default routes on the net2/net3/net4 nodes should make them relatively
easy to configure. It is absolutely not necessary to add scads of per-node
routes by hand; if you use the second alternative for configuring your net1
nodes, per-node routes should be created automatically by the ICMP
Redirects.

Good luck.
--
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warranty is expressed or implied. The information included herein is not to
be contrued as a committment on HP's part. The devil made me do it. This
won't save me from the lawyers' wrath, but it can't hurt.

Jason Zions			The Hewlett-Packard Company
Colorado Networks Division	3404 E. Harmony Road
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