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Cisco CCNA 200-301 v2.0 · Domain 3: IP routing

OSPF adjacency requirements: area, subnet, hello/dead timers, MTU, authentication, unique router ID

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Last reviewed September 30, 2026 · Leer en español

Two OSPF (Open Shortest Path First) routers on the same link will not always become neighbours. OSPF checks several parameters inside hello packets, and some more during the database exchange that follows, and if they disagree the relationship stalls. Knowing each requirement, and the neighbour state where each mismatch leaves the routers, lets you diagnose adjacency problems in seconds rather than guessing, and it is a favourite exam topic.

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