OSPF: LSA Types

Only routers that originated an LSA are allowed to modify it or withdraw it.  Other routers must process and flood that LSA within its defined flooding scope if they recognize the LSA, however they cannot modify it or block up before its Max Lifetime has expired.

Type 1 – Router LSA – One per router per area, flooded only in its area of origin, lists the RId and all interface IP addresses in that area.

Type 2 – Network LSA – One per transit network, created by the DR represents the subnet and the router interfaces connected to the subnet, flooded only in its area of origin

Type 3 – Net Summary – Created by ABRs to represent networks in their attached areas, Defines the subnets in the origin area and cost but no topology information.  Flooded only within its area of origin, and reoriginated on ABRs

Type 4 – ASBR Summary – Like Type 3, but it advertises a host route used to reach an ASBR.  Flooded only in its area of origin, reoriginated on ABRs

Type 5 – AS External – ASBRs flood this into areas used for external routes

Type 6 – Group Membership – Used for MOSPF, not used by cisco

Type 7 – NSSA External – Created by ASBRs in a NSSA, instead of type 5, flooded only within its area and converted to type 5 on ABR to other areas.

Type 8 – External Attributes – Created by ASBRs during BGP to OSPF redistribution to preserve BGP attributes of redistributed networks.  Not used on Cisco Routers

Type 9 through 11 – Opaque – Used as generic LSAs for future extensions.

 

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