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Date: Mon, 31 Jul 2006 15:40:51 -0400
From: "Joseph Gleason" <fireduck@gmail.com>
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Subject: multiple interfaces on same subnet?
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Is it possible to reach two hosts via two interfaces that are both on
the same subnet?

Example:
em0: 172.20.0.1/16
em1: 172.20.0.2/16

And I want to reach 172.20.0.3 via em0 and 172.20.0.4 via em1.

>From 'netstat -nr' I see a line like this:
172.20/14          link#1             UC          0        0    em0

This seems to say that anything on 172.20/14 should be reached on em0.
Is it possible to add a rule that says that 172.20.0.4 should be
reachable on em1?

I only care about the path of outbound packets.  I don't care which
interface inbound traffic comes on.

I am well aware that this is a fairly strange thing to do.

My objective is to have a FreeBSD box balance outbound traffic between
two NICs, while being able to select from among many routers that
could be the default gateway and having the two NICs connect to
different switches for fault tolerance. (I would do the fault
tolerance via a watchdog script of some sort)

If it weren't for the many routers aspect, it would be reasonable to
create separate subnets.  I need to be able to select from a group of
around 10 possible default gateways and some of those routers I do not
control so adding a subnet would be trouble.