What is ‘Administrative Distance’ used for in routing?

Administrative Distance is a vital concept in routing protocols, serving as a metric that ranks the trustworthiness of different routes that a router learns. It reflects the reliability of the source of the routing information. Each routing protocol is assigned a default numerical value for its administrative distance, with lower values indicating more trustworthy routes. For instance, directly connected interfaces typically have an administrative distance of 0, while static routes have a distance of 1, and various dynamic routing protocols have higher distances.

When a router receives routing information from multiple sources, it uses administrative distance to select the best path to a destination. If two routes are available to the same destination but learned from different protocols, the router will prefer the one with the lower administrative distance. This mechanism ensures that the most reliable routes are favored in the routing table, allowing for efficient and effective routing of network traffic.

The other options do not accurately capture the essence of administrative distance. It does not measure network speed, determine bandwidth, or categorize traffic types, which are all different networking concepts. Understanding administrative distance empowers network professionals to make informed decisions about route selection and optimize network performance.