Description: Adjacency in OSPF (Open Shortest Path First) and EIGRP (Enhanced Interior Gateway Routing Protocol) refers to the relationship established between two routers that have successfully established a direct connection and exchanged routing information. In OSPF, adjacency is formed when two routers on the same network or link segment recognize each other and begin exchanging Hello messages, allowing the creation of an adjacency database. This database is fundamental for the route calculation process, as only adjacent routers can exchange link state information and thus build a complete view of the network topology. In EIGRP, adjacency is established similarly, where routers exchange Hello packets to form adjacency relationships and share routing information. Adjacency is crucial for the efficient operation of both protocols, as it ensures that only directly connected routers can communicate and collaborate in determining the best routes for data traffic. Without proper adjacency, routers would not be able to exchange routing information, leading to a lack of knowledge about the network topology and consequently to packet delivery issues.
