Which protocol is commonly used as the interior gateway protocol in enterprise networks?

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

Answer: (A)

Inside an enterprise, routing inside the network uses an interior gateway protocol that all routers in the same domain can understand. OSPF fits this purpose best because it’s an open standard and vendor-neutral, designed to scale to large networks. It uses a link-state approach where routers share their view of the network, allowing every router to build a complete topology map and compute the best paths with Dijkstra’s SPF algorithm. The hierarchical design with areas and a backbone helps manage large networks without overwhelming routers with updates, and it supports fast convergence, equal-cost multipath load balancing, route summarization at area borders, and authentication for security.

RIP is older and based on hop count, which limits scalability and performance in larger networks. BGP is intended for routing between different autonomous systems (external to a single enterprise), not inside it. EIGRP is Cisco-proprietary, which can limit interoperability in multi-vendor environments. For these reasons, OSPF is the most commonly used interior gateway protocol in enterprise networks.