Is it possible to route this way??

[84ian]

I have an NIDS or network intrusion detection system to be set up on my LAN. The NIDS is to be placed in betwn my router and firewall.

i have 3 subnets.
192.168.......
-0.0
-1.0
-2.0

i have installed 3 NICs in my nids machine. currently im testing one of the subnets first. i have managed to ping .1 subnet to .0 subnet. Tried applying the NAT technique and masquerading method but i still cant access the internet when i use a machine on the .1 subnet to access say yahoo.com.

i heard that an private address cant be routed and not sure if it has anything to do with this. Sorry if i sound "duhz" but im a total newbie to all these. Hope some one can guide me along on this.

Probably a lil explanation as well . Thanxs.

[je_fro]

NAT should route all private IP's and make them appear as your actual external IP.
You have a NIDS machine (3 nics) between router and firewall? What router? What kind of firewall? My firewalls are usually a GNU/Linux or BSD machine with multiple nics. Why not put the extra nics in the firewall and route through that?

[84ian]

Router(X.X.0.1)
|
| (192.168.0.0/24)
NIDS machine------------------------------ Lan2
|
|
Lan 1 (192.168.1.0/24)

Forget about the firewall thing first. Presently my nids machine is using redhat 9.0 and can surf the net. im trying to NAT the thing to allow a comp frm say lan1 to access the net through my nids machine. But how do i do that? i've basically typed lots of rules and chains (that's wat they're called right?) using iptables and masquerading, nothing happens.

Maybe anyone could suggest a chain that i could try? Im not vv comp savvy, let alone good at networking. Probably through your help i might start to see the big pic. Thanxs alot.