OSPF LSA Types with Example | GPON Solution

OSPF LSA Types with Example


There are different types of link-state advertisements (LSAs) that would be used for Open Shortest Path First (OSPF). This article contains List of OSPF LSA types with a short description. LSAs build up the OSPF link state database (LSDB), and they are exchanged between OSPF enabled nodes. Bellow short description of OSPF LSA types.

  • LSA Type 1 (Router LSA): LAS type 1 are generated by every router of an OSPF area. They are flooded to all other routers only inside an area of origin & directly connected router. In the link-state ID you will find the originating router’s ID.
  • LSA Type 2 (Network LSA): LSA type 2 are generated by DR  and flooded into the area of origin. The link-state ID will be the router ID of the DR.

  • LSA Type 3 (Network Summary LSA): LSA type 3 are generated by ABR’s sent into an area to advertise prefixes to other areas & flooded throughout the Autonomous System. Type 3 LSAs are sent between two areas to allow inter-area communication.
  • LSA Type 4 (ASBR Summary LSA): LSA type 4 are generated by ABR’s that advertises the ASBR & flooded throughout the Autonomous System. The link-state ID will be the router ID of the ASBR.
  • LSA Type 5 (AS External LSA): LSA type 5 are generated by ASBR that advertises external networks outside the local Autonomous System. Also take the form of a default route to all networks outside the local AS. Type 5 LSAs are flooded to all areas in the OSPF throughout the Autonomous System.
  • LSA Type 6 (Multicast LSA): This type of LSA is used for multicast OSPF applications. Cisco does not support it.
  • LSA Type 7 (NSSA External): LSA type 7 are generated by an ASBR inside a Not So Stubby Area (NSSA) to describe routes redistributed into the NSSA.
  • LSA Type 8 (External attributes LSA For BGP): Used to work with BGP.
  • LSA Type 9,10,11 (Opaque LSAs): For future use.



OSPF LSA Types Message:
  • LSA1s build the Router Link States
  • LSA2s build the Net Link States (O)
  • LSA3s build the Summary Net Link States (O IA)
  • LSA4s build the AS Summary Net Link States (IA)
  • LSA5s build external route information (E1 or E2)


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OSPF LSA Types with Example was last modified: February 4th, 2015 by Shahed



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