[comp.protocols.tcp-ip] Doing default routing on 2 interfaces ???

linegar@bcars85.bnr.ca (Derick Linegar) (08/24/90)

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

neihart@mozart.amd.com (Carl Neihart) (08/24/90)

In article <linegar.651451820@bcars85> linegar@bcars85.bnr.ca (Derick Linegar) writes:
>
>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...

I do not know what kind of router you are using, but if you are using cisco
routers, add an ethernet interface in the router and connect it to the internet
directly.  You will be able to accomplish the necessary routing arrangement very 
cleanly with this setup.  Unfortunately, Unix systems are not designed to have
multiple ethernet interfaces cleanly.


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| Advanced Micro Devices, Inc.                              |
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