3 OSPF Neighbors and Adjacencies Free Online FlashCards

What do OSPF Hello packets do?

Hello packets discover routers and maintain their neighbor relationships.

How does an OSPF adjacency differ from a neighbor relationship?

A neighbor relationship tracks routers that discover one another; an adjacency is the relationship used to synchronize their link-state databases.

What normally happens to OSPF adjacency on a point-to-point network?

On a point-to-point network, the two OSPF routers normally become adjacent.

Why can two OSPF DROther routers remain 2-Way on a broadcast network?

On a broadcast network, DROther routers commonly stay 2-Way with one another and form full adjacencies with the DR and BDR.

Which OSPF settings must match for routers to become neighbors?

They must agree on the Hello and Dead intervals, area, and authentication settings; on broadcast and NBMA networks, their subnet masks must also agree.

What does the OSPF Dead interval determine?

The Dead interval is how long a router waits without receiving a Hello before declaring the neighbor down.

What does the OSPF Init state indicate?

In Init, a router has received a Hello, but that Hello does not list its router ID, so two-way communication is not confirmed.

What happens during OSPF ExStart?

In ExStart, routers negotiate which one begins the database-description exchange and establish sequence numbers.

What do OSPF routers exchange in the Exchange state?

In Exchange, routers send Database Description packets that summarize their link-state databases.

What happens during OSPF Loading?

In Loading, routers request and receive needed or newer link-state advertisements.

What does OSPF Full confirm—and what does it not guarantee?

Full means the adjacency is formed and the link-state database exchange is complete; it does not guarantee that a particular route is installed.

What should you investigate when an OSPF neighbor has no entry?

A missing neighbor entry means no valid Hello has been received. Check link status, OSPF enablement, addressing, area, timers, authentication, and packet delivery.