Newsgroups: comp.protocols.tcp-ip
Path: utzoo!utgpu!cunews!bnrgate!bcars85!linegar
From: linegar@bcars85.bnr.ca (Derick Linegar)
Subject: Doing default routing on 2 interfaces ???
Message-ID: <linegar.651451820@bcars85>
Summary: doing default routing or equiv on 2 interfaces?
Keywords: default routing 
Sender: news@bnrgate.bnr.ca (USENET News System)
Organization: Bell-Northern Research, Ltd. Ottawa Ontario CANADA
Date: 23 Aug 90 22:50:20 GMT


I have an interesting routing question. First the setup:

A hosts with 2 ethernet interfaces, IP forwarding disabled, and not
running any routing daemons, such as routed or gated. I am trying 
to make this host smart by doing default routing & proxy-ARPing on
both interfaces. (See scenario)


Scenario:

		     Internet
		         |
		    -----------
			|
			|
		     +-------+
		     |  A    |
		     | Host  |
		     |  B    |
		     +-------+
			|
			|
		   ------------- 42.128 subnet
		     |
		     |
		  +-------+
		  |  A    |
		  | router|
		  |  B    |
		  +-------+
		     |
		     |
		  Other 42 subnets


Now, I figured by adding 2 default routes (1 for each interface) the
machine would ARP on both interfaces, and whoever responds first, it
will use. No go, as I found out, it will always use the first default
route in the routing table. 

I then decided to do default routing on one interface (A on the hosts) and
tell the machine how to get to network 42 through interface B on the hosts
to the "gateway" router. (route add net 42.0.0.0 router-address-A 1) This
also does not seem to work, as the hosts ARP's on interface A!

I got this setup to work, but by adding manually all the subnets on net 42!
I cannot see this to be an acceptable solution, as we have tons of subnets,
and adding them statically, I consider to be a bad idea (especially when
we have multiple paths to these subnets).

Why can't I add a static route for the hosts, telling it how to route
for all other subnets on 42, (except for the directly connected one) to
the router? I can live with one static route for all other subnets, but
adding one for each subnet is perversive...

				-derick-
--
#include <disclaimer.h>
Derick Linegar,     Internet Systems 4P27,              Bell-Northern Research 
BITNET: LINEGAR@BNR.ca                                  P.O. Box 3511 Station C
UUCP:   ...uunet!bnrgate!bcars85!linegar		Ottawa ONT. K1Y 4H7