After OSPF Router ID changes on the local device, the LSAs received by OSPF neighbors before the change will be invalid. After the OSPF process is restarted, its neighbors will store those invalid LSAs. When the invalid LSAs time out (the age value of those LSAs reaches 3600s), the system deletes the invalid LSAs. Invalid LSAs consume memory resources. If there is a great number of invalid LSAs and the OSPF neighbors are low-end routers with a small memory, service failures may occur. Therefore, you need to clear invalid LSAs of the OSPF neighbors immediately. Run the reset ospf process-id process flush-waiting-timer time command to restart the OSPF process on the local device. After the OSPF process is restarted, OSPF regenerates its own LSAs in a specified period of time and sets the age value to 3600s. The neighbors will immediately delete the invalid LSAs once receiving the LSAs whose age value is 3600s.

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thank you for sharing this useful note

helpful note