What is the administrative distance (AD) for directly connected routes?

The administrative distance (AD) for directly connected routes is 0. This means that directly connected networks are considered the most reliable routes because they come directly from the local router’s interfaces. An AD of 0 indicates that these routes have the highest priority when a router is determining the best path to a destination.

Using this metric, when a router has multiple routes to reach the same destination, it will always prefer the directly connected route due to its AD of 0, even if other routes such as static or dynamic routes with higher administrative distances are available. Understanding this allows network engineers to effectively design and troubleshoot routing protocols, ensuring that their configurations prioritize the fastest and most reliable paths.