Stub/totally stub/nssa/totally nssa

Stub area: LSA type 1/2/3 are allowed, LSA type 4/5/7 are not allowed, no ASBR is allowed default route is injected automatically when stub area is configured on ABR

Totally stub area: LSA type 1/2 are allowed,,a default route is injected automatically, this default route is an only allowed type 3 LSA. LSA type 4/5/7 are not allowed.

Not so stub area: LSA type 1/2/3/7 is allowed, LSA type 4/5 are not allowed, ASBR is allowed. default route need to be configured manually with command: area <area id> nssa default-information originate. This default route will be advertisized as LSA type 7

Totally Not So Stub area: LSA type 3/4/5 is not allowed, LSA type 1/2/7 allowed. default route need to be configured manually with command: area <area id> nssa default-information originate. This default route will be advertisized as LSA type 7

When OSPF do recalculation

1, When there is update of LSA type 1 and type 2, recalculation will be done for the entire routing table,  started with shortest path calculation for each area. not just in the area that link state database has changed.

2, When there is update of LSA type 3, network summary, the recalculation will be done partially. Specially, the destination described in the network summary LSA will be recalculated, if the destination is ABR, it may also need to re-examine all external LSA types.

3, When there is update of LSA type 5 or 7, the destination described in the external LSA will be recalculated.