If a router receives two updates listing the same remote network, the first thing the router checks is the
AD. If one of the advertised routes has a lower AD than the other, then the route with the lowest AD will
be placed in the routing table.
If both advertised routes to the same network have the same AD, then routing protocol metrics (such as
hop count or bandwidth of the lines) will be used to find the best path to the remote network. The
advertised route with the lowest metric will be placed in the routing table. But if both advertised routes
have the same AD as well as the same metrics, then the routing protocol will load-balance to the remote
network (which means that it sends packets down each link).
Table 9.1 shows the default administrative distances that a Cisco router uses to decide which route to take
to a remote network.