OSPF LSA Persistence with DNA flag

OSPF LSAs learned through virtual links can persist in the Link State Database (LSDB) even after removing the virtual link due to the DNA (Do Not Age) flag. When an LSA has the DNA flag set, it prevents the LSA from aging out of the LSDB, causing it to remain indefinitely until explicitly removed, the OSPF process is removed, or the device is reset.

The DNA flag is typically set for LSAs originating from interfaces marked as point-to-point or virtual links to ensure they persist as long as possible across the network.

Clearing the OSPF process may not always remove LSAs marked with DNA, as it usually initiates a soft reset rather than a full teardown of the OSPF database. This process re-establishes neighbor relationships, refreshes LSAs, and recalculates routing tables, but doesn't entirely flush DNA-flagged LSAs from the LSDB.

To completely remove these persistent LSAs, a device reload or removal of the OSPF configuration is necessary.