[lug] routing

Michael J. Pedersen marvin at keepthetouch.org
Fri Jan 12 13:22:32 MST 2001

On Fri, Jan 12, 2001 at 01:34:53PM -0500, Hugh Brown wrote:
> My problem is I'm not sure what I set as the static route.  I tried to
> do
> route add -net gw 
> and it told me that it wasn't feasible.  My thought was that I want all
> traffic destined for the net to use as the
> router.  So what static route can I add (I do only have 3 workstations
> so that will be easiest until I get more savvy about network things).

I'm going to use a (mostly) mythical setup to show you what all you need to
do. If you don't feel like reading all this, here's the short answer:

The box which accesses the 192.168.0 network needs to be configured to route
and masquerade traffic from the 172.16 network. After that, configure any
boxes on the 172 network to use the 172 NIC as their gateway.

Long answer:

A quick diagram of what you haveis here, and I'm going to assign names to the

 ________    ________    ___________    ______
\________/  \________/  \___________/  \______/

Actually, I'm going to name the NICs, since that's what we have to deal with:
IF = Internet to Firewall NIC
FW = Firewall to Workstation NIC
WF = Workstation to Firewall NIC
W1 = Workstation to 172net NIC
1W = 172net to Workstation NIC

IF has a real, routable IP address, usable on the internet.
FW has an ip address in the network, assign it as
WF has an ip address in the network, assign it as
W1 has an ip address in the network, assign it as
1W has an ip address in the network

Problem: Get traffic routed appropriately so that a machine may connect at any
spot on this network, and access any other spot on this network.

Set routes appropriate on each of these nics, and masquerading.

FW should be configured to do masquerading for all traffic passing over it.
This allows traffic to reach the internet.

W1 should be configured to do masquerading, same as FW. Reason being the same.

Anything  which connects onto the 172net should use a gateway of

Anything which connects to the 192 network should use a gateway of

Anything which gets connected to the 192 network should also have a route
added in at boot-time (via rc.local, for instance) which says to use as the route for anything going to network. This
command should do it:

route add -net netmask gw

Michael J. Pedersen
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