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Commonly confused · Routing & Switching

OSPF vs EIGRP: What's the Difference?

OSPF is an open-standard link-state protocol that builds a full topology map and runs Dijkstra's SPF algorithm. EIGRP is a Cisco-developed advanced distance-vector protocol that uses the DUAL algorithm and feasible successors for very fast convergence.

Open Shortest Path First (OSPF)

Full definition
vs

Enhanced Interior Gateway Routing Protocol (EIGRP)

Full definition
Open Shortest Path FirstEnhanced Interior Gateway Routing Protocol
TypeLink stateAdvanced distance vector (hybrid)
StandardOpen standard (RFC 2328)Cisco origin; published as informational RFC 7868
AlgorithmDijkstra SPFDUAL
MetricCost based on interface bandwidthComposite, by default bandwidth and delay
Administrative distance11090 internal, 170 external
HierarchyAreas with area 0 as backboneFlat; summarization anywhere
Multicast addresses224.0.0.5 and 224.0.0.6224.0.0.10
Unequal-cost load balancingNoYes, with variance
Remember it

OSPF maps the whole city; EIGRP trusts its neighbors and keeps a backup ready.

Exam tip

Common items: which protocol is preferred when both know a route (EIGRP, AD 90), which supports unequal-cost load balancing (EIGRP), and which requires area 0 (OSPF).

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