| 1 | Either the IP address or the mask is misconfigured on one of the neighboring interfaces. |
| 2 | One router is configured as a stub area router, and the other is not. |
| 3 | The receiving router is configured for MD5 (type 2) authentication, and the neighbor has no authentication configured (type 0). |
| 4 | The passwords configured on the two routers do not match. |
| 5 | The neighboring interfaces are not configured with the same area ID. |
| 6 | RTA's network statements are in the wrong order. The first statement matches IP address 192.168.50.242 and puts it in area 192.168.50.0. |
| 7 | Link ID 10.8.5.1 is the most likely suspect because its sequence number is substantially higher than the sequence numbers of the other links. |