What are the different types of link-state advertisements (LSAs) that will be used in Open Shortest Path First (OSPF)?
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The following are the types of LSAs you would usually find in an OSPF network:
LSA types found in OSPF networks
| Type # | Name | Description |
| Type 1 | router LSA | A router sends this to describe neighbors and its own interfaces. |
| Type 2 | network LSA | For broadcast networks only; this LSA is flooded by the DR and lists OSPF-speaking routers on the network. |
| Type 3 | network summary LSA | Sent by an ASBR to advertise networks reachable through it. A stub area router will also use this for the default route. |
| Type 4 | ASBR-summary LSA | Sent by ASBR, but only internally. This describes to the others how to get to the ASBR itself, and uses only internal metrics. |
| Type 5 | AS-external LSA | Used to describe external routes to internal areas. Can be used to advertise "this is the way to the Internet" (or some subset of). |
| Type 6 | Group summary | Used in multicast (MOSPF). Ignore this. |
| Type 7 | NSSA area import. | |
| Type 8 | External Attributes LSA | This is very rarely deployed and is used when BGP information is carried across OSPF AS. |
| Type 9, 10, 11 | All are Opaque LSAs. | They are designated for future specifically for application specific purposes. |
This was first published in May 2008