Ubuntu Server - How do I bridge 2 NICs for Firewall?

[Gen2ly]

I'll admit it, I'm a complete dolt when itcomes to networking. I understand the basics but I need a bit of help with this.

I'm building a server for a home network to use as a firewall. The pc has 2 NIC's and I going to have the internet come in one, run it through a firewall and output it through the second NIC to my regular computer.

Going through the documentation (https://help.ubuntu.com/8.10/serverguide/C/network-configuration.html#bridging) step by step and got to this:


Bridging

Bridging multiple interfaces is a more advanced configuration, but is very useful in multiple scenarios. One scenario is setting up a bridge with multiple network interfaces, then using a firewall to filter traffic between two network segments

I got lost in the documentation when it only defines one NIC in /etc/network/interfaces:


auto lo
iface lo inet loopback

auto br0
iface br0 inet static
address 192.168.0.10
network 192.168.0.0
netmask 255.255.255.0
broadcast 192.168.0.255
gateway 192.168.0.1
bridge_ports eth0
bridge_fd 9
bridge_hello 2
bridge_maxage 12
bridge_stp off

So the first question is how do I define the second NIC? I noticed this howto (https://help.ubuntu.com/community/Router) doesn't use bridging. The second question is are there advantages to using bridging (for ease of configuration, maintenance...) or am I just gnawing my own foot?

[Gen2ly]

Ok, I think I got it. After a bit of Research it looks like a bridge is used to define two networks cards simaltaneously. E.g. you have a wired card and a wireless card you'd both like to connect to a LAN network.