ip masquerading/subnets

Mike Wright mike.wright at mailinator.com
Mon Nov 26 22:22:12 UTC 2007

bruce wrote:
> Hi Mike..
> and adding this route to the box2, will allow me to ping box2/eth0 from
> box1?
> or are you saying that i'd have to add the route to box1. if i have to add a
> route to box1, then i'd have to add a route to every box in the system...
> which isn't what i'd want to do.
> again.. thanks for the basic understanding..

I'm not so sure I have that basic understanding ;)

Blaaargh!  The command I gave you was a linux command that can't be 
executed on the windows box, ergo: bad advice.

You mentioned two boxes with one to come, then you mentioned that there 
is also another router (to the internet? connected to box1?).  If so, 
then is this what you have?

internet                     (router's default gateway)
router wan   xxx.xxx.xxx.xxx (your outside IP)
router lan   yyy.yyy.yyy.??? (box1's default gateway)
box1's eth?  yyy.yyy.yyy.??? (box1's other IP)
box1's eth0     (box2's default gateway)
box2's ath0     (box1's route to box2 and beyond)
box2's eth0     (box3's default gateway)
box3 eth0    192.168.2.???/24

Note that each box further from the internet has a default route that 
points to the network device of the next closer box.

Now, in order to have box1 be able to access box2 and further box1 will 
have to have a route added to its routing table that points to box2. 
This is where I gave the wrong command.  You'd have to use whatever is 
the appropriate windows command to add an additional route (ipconfig???).

The only other consideration (ignoring iptables) is that box2 must have 
forwarding enabled or it will not pass traffic between its two interfaces:

     /etc/sysctl.conf -> net.ipv4.ip_forward = 1

Hope that is a little clearer.  :m)

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