Which of the following statements is true about router adjacency in OSPF?

In OSPF (Open Shortest Path First) routing, the concept of router adjacency is crucial for the efficient distribution of routing information. When OSPF operates in broadcast and non-broadcast multi-access networks (like Ethernet), a key mechanism is the election of Designated Routers (DR) and Backup Designated Routers (BDR).

All routers within the same OSPF area will form full adjacency with the DR and BDR. This is because not every router needs to communicate with every other router in the network; instead, they communicate their routing information through the DR and BDR. This design helps reduce the number of adjacencies and the amount of routing information that is exchanged, which enhances efficiency, particularly in larger networks.

Therefore, it is accurate to state that all routers will maintain adjacency with the DR and BDR only, rather than forming full adjacency with every other router in the network. This design minimizes unnecessary overhead and optimizes routing updates. Consequently, the statement that all routers form adjacency with the DR and BDR only aligns with OSPF's operational principles in such network configurations.