Neighbor Stuck in 2Way State

In the topology in Figure 3-35, all routers are running OSPF neighbors over the Ethernet network.

Figure 3-35 Stuck in 2-Way State?

Example 3-18 provides sample output of the show ip ospf neighbor command on R7. Example 3-18 Output from the show ip ospf neighbor Command for Router 7

router-7#show

ip ospf

neighbor

Neighbor ID

Pri

State

Dead Time

Address

Interface

170.170.3.2

1

FULL/BDR

00:00:37

170.170

3

2

Ethernet0

170.170.3.3

1

2WAY/DROTHER

00:00:30

170.170

3

3

Ethernet0

170.170.10.8

1

FULL/DR

00:00:39

170.170

3

8

Ethernet0

170.170.7.4

1

2WAY/DROTHER

00:00:39

170.170

3

4

router-7#

R7 establishes full adjacency only with the DR and BDR. All other routers have a 2-way adjacency established. This is normal behavior for OSPF.

Whenever a router sees itself in a neighbor's Hello packet, it confirms bidirectional communication and transitions the neighbor state to 2-way. At this point, the routers perform DR and BDR election. A router attempts to form a full adjacency with a neighbor if one of the two routers is the DR or BDR. OSPF routers become fully adjacent with routers with which they have successfully completed the database synchronization process. This is the process by which OSPF routers exchange link-state information to populate their databases with the same information. Again, this database synchronization process is executed only between two routers if one of the two routers is the DR or BDR.

This was a trick question to remind you that not everything you see is wrong and to remember the unique aspects of the OSPF.

0323FMf.book Page 158 Wednesday, March 12, 2003 9:41 AM

158 Chapter 3: OSPF Communication

Was this article helpful?

0 0

Post a comment