Unable to Establish Adjacency with Neighboring OSPF Routers

• Microsoft Windows NT Server version 4.0
• Microsoft Routing and Remote Access Service Update for Windows NT Server 4.0

SUMMARY

This article provides troubleshooting ideas for OSPF routers that are not able to establish an Adjacency. An Adjacency is established when the Link State database of neighboring routers is fully synchronized.

1. Ping the neighboring router to ensure basic network connectivity.

2. Windows NT OSPF routers have Authentication enabled by default. The default password is 12345678. Be sure to change the Authentication to match all neighboring OSPF routers. The password is configured on a per- interface basis on the General tab. Passwords are case sensitive.

3. Be sure that the Hello and Dead intervals match the Hello and Dead intervals of neighboring OSPF routers. By default the Hello interval is 10 seconds and the Dead interval is 40 seconds. These intervals are configured on a per-interface basis in the Advanced tab.

4. Be sure that area border routers (ABR) are on the backbone 0.0.0.0. Area border routers are routers that are part of two or more different OSPF areas. An ABR does not have to be physically on the backbone if a virtual link has been created, attaching it to the backbone. Virtual links are configured globally on the Virtual Interfaces tab. Virtual neighbors must be configured using the router ID, not just any IP address.

5. If the routers are on a non-broadcast multi access (NBMA) network, such as X.25 or frame relay, their neighbors must be manually configured because neighbors are unable to be found through multicast. Neighbors are configured on a per-interface basis on the Neighbors tab. Neighbors must be configured using the IP address of the neighbor to which the link state information needs to be sent.

6. If you have an NBMA network, such as X.25 or frame relay, that is in a hub and spoke configuration, be sure to set the router priority on spoke routers to 0 and the hub router to 1 or greater. A router priority of 0 means that the router cannot become a designated router (DR) . The hub router must be the DR because it is the only router that can communicate directly with all other routers. The router priority defaults to 1 and is set on a per-interfaces basis on the General tab

7. On broadcast (token ring, Ethernet, FDDI) or NBMA networks (X.25, frame relay), be sure that all routers do not have a priority of 0. At least one router needs a priority of 1 or greater to become the designated router.

8. Be sure neighboring routers are configured correctly with the same area ID.

9. When you configure an OSPF router, be careful not to duplicate router identification numbers. The router identification number should uniquely identify a router throughout the OSPF autonomous system.