[NMLUG] Multi-Homed Linux and Routing

[ken at lectrosonics.com (Ken Long)]

You're right, you only want one default route. Use a static route for 
the network on eth1. You'll probably have to use static config on 
eth1 rather than dhcp.

Here's my setup on an *old* Slackware box:

# "outside" net card
/sbin/ifconfig eth0 204.134.115.226 broadcast 204.134.115.255 netmask 
255.255.255.224

/sbin/route add -net 204.134.115.224 netmask 255.255.255.224 eth0

/sbin/route add default gw 204.134.115.225 netmask 0.0.0.0 metric 1

# "inside" net card
/sbin/ifconfig eth1 172.16.2.18 broadcast 172.16.2.255 netmask 
255.255.255.0

/sbin/route add -net 172.16.2.0 netmask 255.255.255.0 eth1

# (Single static route for entire company.)
# (Note: the netmask needs to be 255.255.0.0 to work. --K.L. 6-7-
2005)

/sbin/route add -net 172.16.0.0 gw 172.16.2.1 netmask 255.255.0.0 
eth1

Ken Long
Lectrosonics, Inc.

On 31 May 2006 at 9:03, Tim Emerick wrote:

> I've posed this question before but without knowing the proper 
> terminologies. I've since experimented and have become stuck. I'm 
> using Debian testing.
> 
> I'm trying to create a proxy server to bridge between two lans.
> 
> eth0 is on lan0 and where all of my traffic should be coming/going. 
> It autoconfigured DNS/gateway from the DHCP server on lan0. It 
> should be my only default gateway.
> 
> I installed eth1 and hooked it to lan1. Linux autoconfigured it with 
> it's own DNS service/gateway from the lan1 DHCP server. I installed 
> tinyproxy and specified incoming from lan0 and outgoing to lan1. 
> Only traffic on eth1 should be from/to tinyproxy only.
> 
> Existing services started really bogging down and I found that it was 
> because linux was trying to decide which lan/route to use because now 
> I had 2 default routes. I want only one default route...lan0.
> 
> What next? What info do I need to provide to clarify my problem?
> 
> For now, I've disabled eth1 so my existing services can run 
> unhindered.
> 
> Thanks!
> 
> Tim
> 
> I'm confused.