How does OSPF handle route loops?

OSPF, or Open Shortest Path First, employs a methodical approach to prevent route loops primarily through the use of sequence numbering and an aging mechanism for Link-State Advertisements (LSAs). Each LSA that OSPF generates carries a sequence number, which is unique for that particular update. This sequence number allows routers to determine the freshness of the information they receive from other routers.

When a router receives an LSA, it checks the sequence number against the LSA it has in its database. If the received LSA has a higher sequence number, it indicates that the information is more recent and valid; therefore, the router updates its database and propagates this information. Conversely, if the sequence number is lower or identical, the LSA indicates old or stale data, and thus, the router can ignore it, effectively preventing the use of outdated or redundant routes that could create loops.

Additionally, the aging mechanism causes LSAs to have a limited lifespan; if an LSA is not refreshed or updated within a specific period, it is considered invalid and removed from the routers' databases. This ensures that even if a route becomes invalid due to topology changes, it will eventually be purged, reducing the chances of persistent loops.

This process