Router help request

Brian Chee chee at hawaii.edu
Thu Dec 27 18:45:45 PST 2001


Here's one of the BIG issues of getting a plain vanilla
linux/bsd/solaris/etc box to be a router....they normally don't talk routing
protocols like RIP/OSPF/BGP/etc.....so you literally have to create a static
route both in the unix'ish box and in the upstream router.

Crude diagram:

world -------- upstream router ----------- linux box ----------
hub/switch ------inside pc's
                      static route                         static route
                      points to linux                    points upward


So you set the default route on the linux box.....and the upstream router
has a static route to the inside pc's subnet....most of the time you MUST
route on whole subnets....depending upon how old a kernel you're
running...you may also have to route on 8bit boundries....

So for instance....I'm running an LRP (linux router project) that boots from
a floppy....for that I'm running two halves of a class "C" subnet.....the
upstream router has two static routes....

xxx.xxx.125.0/25 via xxx.xxx.190.200/24
xxx.xxx.125.128/25 via xxx.xxx.190.190/24

Translated, get to the xxx.xxx.125.0/25 (aka bottom half of the subnet) via
xxx.xxx.190.200
to get to the xxx.xxx.125.128/25 (aka the top half of the subnet) via
xxx.xxx.190.190

All you're doing is having the upstream point to the "hidden" subnet.....

Take a look at Zebra...it's a linux/bsd based soft router that talked
rip/ospf and can automagically tell the upstream routers about your
networks...

/brian chee


University of Hawaii ICS Dept
Advanced Network Computing Lab
1680 East West Road, POST rm 311
Honolulu, HI  96822
808-956-5797 voice, 808-956-5175 fax

----- Original Message -----
From: "Brian Hessee" <gasp at runbox.com>
To: "Linux & Unix Advocates & Users" <luau at maile.hi.net>
Sent: Thursday, December 27, 2001 1:03 PM
Subject: [luau] Re:Router help request


> Aloha all,
>
> I hope everyone's holiday went well, mine did.
>
>
> I built a box to use as a router recently and am in need of some help to

> get it to function as a router.  What I have is a K6-2 500 and 2 NICs
> with a hard drive etc..  I have installed RH 7.2 from CDROM and
> MonMotha's firewall rules.  I can't get it to route though.  It appears
> to connect to the 'net OK by itself, but I can't get any other computers
> to connect through it.  Any ideas???
>
> Thanks in advance,
>
> Ben
>
just out of curiosity ( and since you didn't mention it ) are the other
computers
being told to look to the router as their way outside?

i know that's probably a dumb question, but i've done the same thing on
occasion...
especially getting windows boxen to look through them seems to be
problematic

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