Re: Routing problem

[Mike Bird <mgb-debian@yosemite.net>]

On Mon, 2006-02-13 at 13:43, jb701@uku.co.uk wrote:
> I cannot get my linux box to act as a router, I'm hoping someone can help. 
> 
> My setup is sarge on a machine with 2 NICs, 192.168.1.2 and 192.168.2.1. 
> 
> I attach 192.168.1.2 to another machine with 2 NICs [192.168.1.1 and 
> 192.168.0.6].  This is a Win2K machine, and it routes connections from the 
> linux box to other machines on the 192.168.0.0/24 network. 
> 
> I now want to attach another machine [192.168.2.2] to 192.168.2.1.  This 
> machine [192.168.2.2] can ping either NIC in the linux box, but it cannot 
> contact machines beyond it. 

Your network looks like this:

 .------.   .-----------.   .-----------.
 |   A  |   |     B     |   |      C    |   
 | .2.2 +---+ .2.1 .1.2 +---+ .1.1 .0.6 +--- .0.*
 `------'   `-----------'   `-----------'

When you attempt to send a packet from .2.2 to .1.1, how does system A
know where to send it?

Assuming such a packet reaches .1.1, how does system C know where to
send the reply?

You may need some routes.  Perhaps these will allow A and C to talk.

On A#  route add default gw 192.168.2.1
On C#  route add -net 192.168.2.0/24 gw 192.168.1.2

You have four or more hosts on three or more network segments.  I'd
strongly recommend an introductory networking course or book.  With
a firm understanding of the principles there's no limit to what you
can achieve.

--Mike Bird