When looking at a router’s configuration, you may notice multiple default routes, each with a specified administrative distance (AD), using the “ip route” command. This can sometimes lead to confusion about two issues: First, why the route with a higher AD isn’t chosen, and second, why multiple default routes are defined if only one will be used.
For the first issue, AD measures the degree of reliability in routing protocols, and can also be entered as a parameter for routes when using “ip route.” However, a lower number means greater reliability. Hence, it’s the route with the lower number that will be favored.
As to multiple default routes, these can provide failover functionality, to help ensure that traffic can still pass through if the preferred route isn’t available.