What is the AD for IS-IS routes?

The administrative distance (AD) is a value used by routers to determine the trustworthiness of the source of routing information. For IS-IS (Intermediate System to Intermediate System) protocols, the administrative distance is set to 115. This value indicates how reliable IS-IS routing information is compared to other routing protocols.

Understanding the importance of AD is crucial in network routing, as it helps in the decision-making process when multiple routes to the same destination are available from different protocols. The AD assigned to IS-IS is lower than that of other routing protocols such as EIGRP, which has an AD of 170, and bgp that is significantly higher, thus making IS-IS more preferable in a scenario where both IS-IS and EIGRP might provide a route to the same destination.

IS-IS routes, due to their lower AD compared to others, are prioritized by the router, which will choose the path provided by IS-IS over those from protocols with a higher AD. This makes IS-IS a valuable protocol in certain enterprise networks where efficiency and reliability in routing are critical.