Which protocol is typically considered a link-state routing protocol?

• A. OSPF
• B. RIP
• C. BGP
• D. EIGRP

Answer: (A)

Link-state routing protocols keep a complete map of the network and use that map to compute routes independently at each router. In this approach, every router floods information about its direct links to all other routers in the area, creating a shared topology database. Each router then runs a shortest-path calculation (typically Dijkstra’s algorithm) on that topology to determine the best routes. This leads to fast convergence and scalable networks because decisions are made from a full view of the network.

OSPF is the classic example of this approach: routers exchange link-state advertisements to build a common view of the network topology, store it in a topology database, and use the shortest-path-first algorithm to compute routes.

RIP, by contrast, uses a distance-vector method, where routers share their routing tables with neighbors and rely on hop count as the metric, with periodic updates and limited scale. BGP operates as a path-vector protocol, focusing on policies and the AS path rather than a full network map. EIGRP is considered a hybrid protocol that blends distance-vector ideas with some features from link-state, but it’s not the pure link-state model like OSPF.

So, the protocol that is typically considered link-state is the one that builds a network-wide topology and uses a shortest-path calculation to determine routes.