Simple question regarding OSPF

[grant.orchard]

Hey guys,

Just started studying for my routing exam and was wondering if someone can explain the concept of adjacencies when discovering routes? Is an adjacency formed simply when two routers are directly connected?

1---2

| |

3---4

Hence would that mean that 1 and 4 are not adjacent? (2 should be connected to 4)

Thankyou

[jeffrey.zhou]

Only directly connected routers will form the adjacency except the virtual link. On Point-to-point or point-to-multipoint network, the directly connected routers always form the adjacencies with the neighbors. and on broadcast or NMBA networks, the routers will only form adjacencies with DR and BDR.

Regards

Jeffrey

[grant.orchard]

So in a NBMA they don't have to be physically adjacent to form adjacencies? Any router within the same area will form a "logical" adjacency with the DR and BDR?

Thankyou

Grant

[jeffrey.zhou]

NO,

Only the routers that attached to the NBMA cloud would form adjaceny.