DR / BDR
2-Way is a healthy boundary
Some neighbors do not need a deeper relationship.
Okay, but what does it mean?
On a broadcast network, two DROther routers normally remain 2-Way with each other. They form full adjacencies with the DR and BDR. Before troubleshooting a state, check whether that adjacency is supposed to form.
Protocol reference: RFC 2328 (OSPFv2). NSSA reference: RFC 3101.