ip masquerading/subnets

[Mike Wright]

bruce wrote:
> hi john...
> 
> i might be missing/lost some emails... so let me start at the very
> beginning!! bear with me if you find yourself repeating something you've
> already stated...
> 
> my initial system (two boxes, nothing between them)
> 
> windows                       linux
> box1     ----- >>> ------      box2 >>>>>> (future separate lan box)
>   eth0    (wireless)      ath0      eth0
> 
> box1
> eth0 - 192.168.1.3
> 
> box2
> ath0 - 192.168.1.5
> eth0 - 192.168.2.5
> 
> from box1, i can ping 192.168.1.5
> from box1, i can't ping 192.168.2.5
> 
> from box2, i can ping box1 (192.168.1.3)
> 
> so, what do i/should i do to connect/ping box2/eth0 from box1?

The linux box is now a router and from the point of view of box1 ath0 is 
just another gateway.  box1 needs to know about any routes available to 
it and it apparently already has a default route which points to your 
first router.  default routes are the ones taken when the desired 
desitination ip is not already specified in the routing table(0).  Since 
you know where 192.168.2.5 is you can add a specific route for that and, 
in fact, since you want to add a future box to that lan, and assuming 
it's a /24 bit netmask, you would use something like this:

(as root)
/sbin/ip route add 192.168.2.0/24 via 192.168.1.5 dev eth0

hth,
Mike Wright