LinuxQuestions.org - Please point to the right "M" so I can "RTFM"

Hi Group,

I'm totally happy with my linux routerbox, and it's now time to expand its services.

Current setup:

eth0 connects to the WWW
eth1 connects to the LAN

eth0 gets its IP address by way of DHCP from my ISP.
eth1 is the gateway, and all the LAN clients use static IP addresses.

I want to add a new subnet using a 3rd NIC: eth2.
I want the LAN clients on subnet eth2 to be able to access the internet via eth0, and also access the Samba server on subnet eth1.
But, I want to block all traffic from subnet eth1 to eth2.

I can't get a handle on what I need to use and/or configure to add another subnet.

Do I need to use routed, or named, or can I do want I want using iptables?
Or do I need to use all three of these and other stuff too?

Thus, I ask you to vigorously tell me "RTFM!" -- however, please remember to state which "M" or "M's".

Thanks,

Mike