Symptom

When using OSPF HELLO timers set to 1 second, with a dead interval of 3 seconds, intermittently the OSPF adjacency will flap across multiple neighbors and VRF instances at the same time.

Conditions

This issue occurs if the OSPF HELLO timers are set to 1 second with a dead interval of 3 seconds and many routes within the NSSA are removed at the same time.

Workaround

- Increase the OSPF HELLO timers to the default setting of 10-second intervals with a 30 second dead timer. or - Upgrade to a 5.x or later release.

Further Problem Description