The big problem with OSPFv2 is the Router LSA which carries many informations through Link Types 1 2 3 ( Neighboring p2p or transit network, virtual link ) in addition it lists all IP prefixes for links in p2p with Link Type 4. Any changes of Link Types ( 1 2 3 4) triggers Full SPF calculation. OSPFv3 improves SPF calculation by removing IP prefixes from Router LSA and gives the responsability to Type-9 LSA so that only when a router lost its neighbor then full SPF is triggered since it impacts all routes through this neighbor while any change of IP prefixes ( new prefix added or old prefix removed) in the Type-9 LSA will not trigger Full SPF calculation. Changes of IP prefixes occurs more frequently than losing the neighbor router.
Another reason for this evolution is that in OSPFv2 a large Router LSA with many links can be flooded with the risk to exceed the MTU .
Removing the IP prefixes from Router LSA in OSPFv3 reduces the size of this LSA making flooding more optimized.
Removing the IP prefixes from Router LSA in OSPFv3 reduces the size of this LSA making flooding more optimized.
