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I have read other posts and google on this but I am still stuck... hoping a new one will help

I am attempting to setup a Linux (Fedora 14) firewall between my wireless router and external modem. I have the machine built and it has 2 network cards and fedora is installed and ready to go.

I have installed DHCP and DNS, but they are not yet configured...

How do I configure the machine to pass traffic from eth0 to eth1? I think I can get iptables going if I could just get this first step done.

I hope this question makes sense.

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closed as off topic by womble, mailq, Steven Monday, Bart De Vos, dyasny Oct 12 '11 at 9:41

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how do you minus one a question? – Siriss Oct 8 '11 at 23:36
I switched to Ubuntu. I am stuck on the idea of the passthrough. I can picture it in my head but editing the /etc/network/interfaces file is giving me trouble. I wrote a comment below. – Siriss Oct 11 '11 at 0:13

This is my basic template for firewall on an ubuntu machine, I think this works on fedora as well

iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables --table nat --delete-chain

echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -F

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i eth1 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

I save it on a file in /etc/init.d/ and make a symlink to /etc/rc2.d, change mode to +x. You can also opt to DROP all packets forwarded to eth1 and open selected ports only.

For DHCP, the following is a basic template, add it inside your dhcpd.conf

subnet netmask {
option routers;
option broadcast-address;
option subnet-mask;
option domain-name-servers;

host YourServer {
hardware ethernet <your-internal-nic-MAC-address>;

As for DNS, insert your service provider's DNS IPs on /etc/resolv.conf and in /etc/bind/named.conf.options. You can also use Google's public DNS IPs or OpenDNS.


The following should be on your /etc/network/interfaces

auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet static

Since your eth0 is on DHCP and I assume is connected to your modem (internet interface), it will request for the IP and Gateway addresses from the modem. The eth1 will be your internal-network interface and is on static IP.

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thanks! I will see if I can get this working. – Siriss Oct 8 '11 at 22:28
I switched to Ubuntu. Fedora was a pain. So I realized that it was not working as stated earlier. The firewall configuration is working, but I had the computer setup incorrectly and now it is still not passing traffic through. I am editing the /etc/network/interfaces and I am curious as to how I set eth0 to have a dynamic IP, gateway and subnet. Then have eth1 have a static IP, subnet, and gateway. I hope this makes sense... or if I am completely doing this wrong I would love to learn Thank you! – Siriss Oct 11 '11 at 0:12

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