LSA Types

Type 1 – Router
Tells the other routers about directly connected links
Type 2 – Network
When routers are in a multiaccess network (think ethernet connection with DR election), the lead router, the “designated router” or DR tells other routers about the multiaccess network connections.
Type 3 – Summary
(Tricky name not actually summarized routes) When LSA Type 1 & 2 are re-advertised into another area, they are converted to type 3 “summary” routes. These type 3’s would also be re-advertised into any areas that they didn’t source from.
Type 4 – ASBR Summary
This one is a bit confusing, it advertises the route to an ASBR router, it is only needed when the ASBR isn’t directly connected to a specific area.
Type 5 – Autonomous system external
An ASBR tells other routers about a router redistributed from outside OSPF, gets re-advertised to all (normal) areas.
Type 6 – Multicast
Type 7 – NSSA
In an NSSA, this type of LSA gets generated instead of a type 5 route, then gets converted to a type 5 LSA when going into another area.
Type 8 – External attribute for BGP

Area Types

Backbone area (area 0)

Standard area

Stub area

Totally stubby area

Not-so-stubby area (NSSA)

In progress… to be continued