I am using an old laptop computer and I have two network connections, eth0 (wired) and eth1 (wireless). I have been looking around on google, but so far I have found no way to configure firestarter, the linux firewall, with two possible network connections. I really dont understand why it is limited to configuration for one device. I mean, cant I have the same rules for both devices, and than firestarter can simply apply them to whichever device is being used? Is this only a problem with firestarter, and can be avoided by using other linux firewalls, like iptables or guarddog? Thanks!

Using two internet devices brings a huge number of questions about which connection to put traffic through. The combination of rules is beyond the scope of a user's tick box scenario. It belongs in the realm of traffic shaping, and because there are many ways and many algorithms to do this, no-one has offered a free to use interface for bandwidth control.

It starts with the ip programme.
Have a read of the Advanced Routing HOWTO to get the interfaces working both directions, then copy and rename the rules from one internet interface to the other.
With the rules active, do iptables-save >> rules.iptables
Copy and rename from this file.
Load the full list with iptables-restore << rules.iptables
This will clear and insert the rules from the file named.