I am bridging 2 networks, but only want the Bridge machine to see both networks.
 

I need a server that is visible from 2 networks. I think I just solved my own question.

I have a network of Phone agents who need access to the database server, but no external access. They run Winblowz. This was fine, because the database was also offline. But Now, we are adding a server that is accessible from the WWW so that different iso's can connect to use and send us data that we can use on our internal network.

I've set up a bridge using bridge-utils and brctl, and would like to know how i can use iptables to filter traffic out so that the networks dont see each other. but i guess what i should really do is leave each nic configured individually, but in that case help me here:

NIC A: 192.168.1.50

NIC B: 192.168.1.90 (i know, should be on a diff subnet, w/e)

How can I use iptables to say (when i connect to machines 192.168.1.1-50, use eth0, and 192.168.1.51-200 use eth1.

Also you think I should just change the subnet of one of the networks?

also what do i need to know about ipforwarding? thank you guys!

actually what you would want to do is set it up as such

internet router->DMZ->firewall->internal network(including database server)
webserver---------|

this would be accomplished by attaching a switch to the router and having your firewall plugged into one port and your webserver attached to another

the webserver and firewall's external nic would be something like 192.168.1.x then forward web traffic to the ip of the webserver
the internal network on the internal nic of the firewall would be something like 10.0.0.x

you can talk to the webserver from inside out but the firewall would prohibit web trafic from outside in

for a firewall look into something like smoothwall which is a custom distribution of linux designed to be a firewall that provides a nice web based interface on it's internal nic