OSPF LSA Types

OSPF LSA Type 1: Router LSA

  • flooded within the area
  • generated by each router
  • the Link State ID = the router ID of the sending router
  • provides information about directly connected networks

OSPF LSA Type 2: Network LSA

  • flooded within the area
  • Link State ID = the IP address of the interface of the network DR

OSPF LSA Type 3: Summary LSA

  • generated by ABRs
  • Link State ID = the IP address of the destination network
  • does not contain summary routes by default. Each subnet is, by default, advertised individually. So if we want to summarize routes, we should configure them manually on ABRs.

OSPF LSA Type 4: Summary LSA

  • generated by ABRs wen there is an ASBR within their¬†area
  • Link State ID = the router ID of the described ASBR
  • some special bits to note here:
    • the e bit (external bit): set by ASBR when forwarding his LSA (Type 1)
    • the b bit (border bit): set by ABR

OSPF LSA Type 5

  • Link State ID = the IP address of the destination network
  • provides information about other Autonomous Systems

OSPF LSA Type 7

  • Link State ID = the IP address of the destination network
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