What type of routing protocol is IS-IS classified as?

IS-IS, or Intermediate System to Intermediate System, is classified as a link-state routing protocol. This classification is based on how IS-IS operates to determine the best path for data through a network.

Link-state protocols function by having each router in the network create a map of the network topology. Each router sends link-state advertisements (LSAs) to inform other routers of its connected networks and the state of those links. IS-IS uses this information to build a complete and synchronized view of the entire network, allowing routers to calculate the shortest path to each destination based on a common algorithm, typically Dijkstra’s algorithm.

The link-state nature of IS-IS allows it to efficiently handle large and complex networks. Each router independently calculates the shortest path based on the information it has gathered, leading to quicker convergence and better overall performance compared to distance-vector protocols, which determine paths based on the cost or distance to reach a destination and exchange this information periodically.

Understanding that IS-IS is a link-state protocol highlights its implications in network configuration and management, especially for large service provider networks and enterprise environments where scalability and rapid convergence are critical.