2 LANs, 1 single gateway, how to separate the LANs?

[cristinsimion]

I have a Fedora Core 1 server, which I use as my internet gateway, with tho ethernet cards: one to the LAN (IPs 10.0.0.x/255.255.255.0) and the other to the Internet.
Recently I added the third ethernet card - for a second LAN (IPs 10.1.0.x/255.255.255.0) which should have access to the internet too through this gateway. The name added by default for the third ethernet card is dev10075 - not eth2 as I expected.
Using the iptables firewall I tried to separate the two LANs but the idea doesn't seem to work. The firewall rules which I added for this are:
iptables -A INPUT -s 10.1.0.0/24 -d 10.0.0.0/24 -j DROP
iptables -A INPUT -s 10.0.0.0/24 -d 10.1.0.0/24 -j DROP
I tried to put these rules in the FORWARD chain or the OUTPUT chain but still I can ping from one LAN to an address in the second LAN.
How can I isolate them? Is the name of the third eth card the problem?

[df12]

IPTables is a wonderful thing... So they say... Sometimes it seems more like Voodoo to me. But I think you'll want to put those on the OUTPUT chain and add the device. Assuming eth1 is connected to the 10.0.0.0/24 network and dev10075 is connected to the 10.1.0.0/24 network

iptables -A OUTPUT -s 10.1.0.0/24 -d 10.0.0.0/24 -o eth1 -j DROP
iptables -A OUTPUT -s 10.0.0.0/24 -d 10.1.0.0/24 -o dev10075 -j DROP

Of course I could be totally wrong

[cristinsimion]

It worked when I moved those rules to the FORWARD chain.