The networking diagram is as follows:
NE5000E ----- SE400 (connected through the GE link). OSPF runs in Area 2 between the NE5000E and SE400.
However, when the NE5000E and SE400 are configured, it is found that the OSPF neighbor between them stays in the Exchange state instead of turning Full.
1. Viewing the configuration of the NE5000E, the engineer found no problem.
2. Pinging the IP addresses under the SE400 on the NE5000E, the engineer found that the small packets were normal, but the large packets (1500) were not.
3. Viewing the port status of the NE5000E, the engineer found no wrong packets.
4. Asking the customer to view the data configuration of the SE400, the engineer compared the configuration with that of the NE5000E and found the MTU value of the GE interface on the SE400 was 1548 instead of the default value 1500.
5. Modifying the MTU value of the GE interface on the NE5000E to 1548, the engineer viewed the status of the OSPF neighbor and found that it turned Full.
6. The SE400 could learn the OSPF routes normally.
1. The data of the NE5000E is misconfigured.
1. The data of the SE400 is misconfigured.
3. The version of the NE5000E does not match that of the SE400.
1. This is a problem related to the MTU value. If the MTU value of a neighbor is larger than that of the local router, the neighbor sends an MTU packet to update the link status. This packet does not reach the local router. Therefore, the OSPF neighbor stays in the Exchange state.
2. It is recommended to give corresponding prompts when creating the OSPF neighbor if the MTU values are inconsistent.