I have to setup dead gateway detection on a linux box with three network interfaces. The only guides I have found so far on the topic imply patching the kernel, which we are not very keen to do. Is there any other way?
Edited to clarify
The 3 interfaces are: 1 Ethernet, 1 wifi and 1 3G modem. The wired is the main connection and the other two are for backup purposes, being the 3G modem the last resource.
High availability is not an issue as we can afford getting disconnected for short periods of time.
The box is at the same time client (sends data to a central server) and server (the central server can change its configuration) and makes public it's current IP by a dyndns-like mechanism.
At the end we will have hundreds of boxes reporting to one central server so the maintenance on the boxes should be as low as possible.