Border Gateway Protocol (BGP) is considered a ______________protocol.

• A. Distance Vector
• B. Link State
• C. Path Vector
• D. Hybrid

Answer: (C)

BGP is a path-vector routing protocol. It makes routing decisions based on the path information that accompanies each route, specifically the sequence of autonomous systems the route has traversed, stored in the AS_PATH attribute. As a route advertises through different autonomous systems, each system appends its own AS number to the path. This path gives both visibility into the route’s lineage and a straightforward way to detect loops—if a router sees its own AS listed in the AS_PATH, it knows the route would loop and can discard it. The path-vector approach also underpins policy-based routing: networks can influence route selection using attributes like AS_PATH, LOCAL_PREF, and others. This is distinct from distance-vector, which relies on hop counts or metrics, and from link-state, where every router builds a full map of the network and computes best paths. BGP is designed for interdomain routing across many different administrative domains, where loop avoidance and routing policies are crucial, making path-vector the right classification.