Routing Protocol Basics
You should know some important facts about routing protocols before getting deeper into
RIP. Specifically, you need to understand administrative distances, the three kinds of routing
protocols, and routing loops. I’ll cover each of these in more detail in the following sections.
Administrative Distances (ADs)
The AD is used to rate the trustworthiness of routing information received on a router from
a neighbor router. An AD is an integer from 0 to 255, where 0 is the most trusted and 255
means no traffic will be passed via this route.
Table 3.6 shows the default administrative distances that a Cisco router uses to decide
which route to take to a remote network.
TABLE 3 . 6 Default Administrative Distances
Route Source Default AD
Connected interface 0
Static route 1