Which routing protocol was originally Cisco proprietary, now open standard, and uses a composite metric with fast convergence?

Which routing protocol was originally Cisco proprietary, now open standard, and uses a composite metric with fast convergence?

• A. EIGRP
• B. IS-IS
• C. RIP
• D. OSPF

Answer: (A)

This question focuses on a routing protocol that combines multiple path characteristics into one metric and converges quickly after changes. The protocol that fits is the one developed by Cisco and later standardized as an open protocol. It uses a composite metric, weighting factors like bandwidth and delay (with optional components such as reliability and load), rather than just counting hops. This allows smarter path selection that reflects real link quality, not just the number of routers traversed. Fast convergence comes from the DUAL algorithm, which computes loop-free paths and enables rapid updates. It uses concepts like feasible successors to keep backup routes ready and diffusing updates so only affected neighbors recompute, minimizing disruption when a link or neighbor changes. Other protocols mentioned don’t fit as cleanly: one is a pure hop-count metric and has slower convergence characteristics, another pair are open-standard link-state protocols with different design philosophies, and neither originated as Cisco proprietary protocols.

This question focuses on a routing protocol that combines multiple path characteristics into one metric and converges quickly after changes. The protocol that fits is the one developed by Cisco and later standardized as an open protocol. It uses a composite metric, weighting factors like bandwidth and delay (with optional components such as reliability and load), rather than just counting hops. This allows smarter path selection that reflects real link quality, not just the number of routers traversed.

Fast convergence comes from the DUAL algorithm, which computes loop-free paths and enables rapid updates. It uses concepts like feasible successors to keep backup routes ready and diffusing updates so only affected neighbors recompute, minimizing disruption when a link or neighbor changes.

Other protocols mentioned don’t fit as cleanly: one is a pure hop-count metric and has slower convergence characteristics, another pair are open-standard link-state protocols with different design philosophies, and neither originated as Cisco proprietary protocols.