I have a wired (eth0) connection and a wireless (wlan0) connection to my router (which in turn connects to the internet). The two connection are setup with different static IPs. I have no problems connecting to the internet with each respective connection. But it involves mannually setting the default gateway everytime I want to switch between interfaces. I was wondering whether it is possible to set it up such that it will look at both connections (in round-robin-style), without explicitly switching between one to another. Namely, if I'm currently connected to the internet through eth0, and I disconnect the ethernet cable, can it automatically switch to use wlan0 to go on the internet? Any help would be appreciated. Thanks.

With Mandriva (which to my knowledge relies on IP links, and hotplug), I achieved this using standard Mandriva GUI tools:

Both eth0 and wlan0 are started on boot. When I connect the ethernet cable, the interface goes up, and route is auto-configured; when I disconnect the cable, route is flushed. Same with wlan0 when I plug/unplug the USB WiFi adapter.

I don't know all the details, but if you want me to look at some config files (eg: in /etc/sysconfig), please ask

Now, the really cool trick would be to bind eth0 and wlan0, so that when both are plugged you have double bandwidth Eg:
my laptop only has USB1.1, so max. 11Mb/s WiFi, and a 10baseT pcmcia card, so max. 10Mb/s. The combination of both could lead to 20Mb/s I guess

Yves.

Umm.. too bad I'm using Gentoo. I wonder what mechanism they use to detect whether the ethernet cable is plugged, or the PCMCIA card is plugged. I tried playing around with /etc/pcmcia, but it doesn't seem to do the trick. It's unconceivable how no one thought of this for Gentoo... I keep thinking to myself that it must already be implemented somehow...

In Moonshine(Fc7), "NetworkManager" does this. It detects link status and runs the necessary scripts to switch networks.