OSPF Basic

OSPF LSA types
LSA Type 1 (Router LSA)
Generated by all routers in an area to describe their directly attached links (Intra-area routes).These do not leave the area.

LSA Type 2 (Network LSA)
Generated by the DR of a broadcast or Nonbroadcast segment to describe the neighbors connected to the segment.These do not leave the area.

LSA Type 3 (Network Summary LSA)
Generated by ABR to describe/advertise a route to neighbors outside the area. (Inter-area routes)

LSA Type 4 (ASBR Summary LSA)
Generated by ABR to advertise a route for/to an ASBR to neighbors outside the area

LSA Type 5 (External LSA)
Generated by ASBR to describe routes redistributed into the OSPF area.These routes appeared as E1 or E2.E2(default) uses a static cost throughout OSPF domain as it only takes the cost into account that is reported at redistribution.E1 uses a cumulative cost of the cost reported into OSPF domain at redribution plus the local cost to the ASBR.

LSA Type 6 (Multicast LSA)
Not supported on Cisco routers.
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Unlike EIRGRP, OSPF does not support route summarization anywhere everywhere. It only supports in Area Border Router (ABR). - external route advertisement.

Stub area blocks route updates coming from any external network (redistribution). It only accepts route updates from Area 0, Area 1, so on. ABR generates a default route to this area.

Totally stubby area block external route advertisement and route advertisements from other Areas. It only knows about routes in its own area. ABR generates a default route to this area.