This module manages the default route.

Devices with more than one network interface may have more than one way of reaching the Internet. The routing table decides which interface an IP packet should use by looking at the "default route" entries. One interface is chosen.

Since not all interfaces are equal, we'd like Linux to pick the fastest and lowest latency one. for example, one could prefer wired Ethernet over WiFi and prefer WiFi over a cellular connection. This module lets you specify an ordering for interfaces and sets up the routes based on this ordering.

This module also handles networking failures. One failure that Linux can't figure out on its own is whether an interface can reach the Internet. Internet reachability is handled elsewhere like in the ConnectivityChecker module. This module should be told reachability status so that it can properly order default routes so that the best reachable interface is used.

IMPORTANT: This module uses priority-based routing. Make sure the following kernel options are enabled:

CONFIG_IP_ADVANCED_ROUTER=y
CONFIG_IP_MULTIPLE_TABLES=y