OSPF - OSPF Design and LSAs - LSA Types

6 important questions on OSPF - OSPF Design and LSAs - LSA Types

Describe the 1-router LSA

One per router per area, listing the router's RID and all interface IP addresses in that area. Represents stub networks as well. Flooded only within its area of origin

Describe the 2-Network LSA

One per transit network. Created by the DR on the subnet, and represents the subnet and the router interface connected to the subnet. Flooded only within its area of origin.

Describe the 3-Net Summary LSA

Created by ABRs to represent networks present in one area when being advertised into another area. Defines the subnets in the origin area, and cost, but no topology data. Flooded only within its area of origin, reoriginated on ABRs
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Describe the 4-ASBR Summary LSA

Like a type 3 LSA, except it advertises a host route used to reach an ASBR. Flooded only within its area of origin; reoriginated on ABRs

Describe the 5-AS External LSA?

Created by ASBRs for external routes injected into OSPF. Flooded to all regular areas

Describe the 7-NSSA External LSA?

Created by ASBRs inside an NASSA, instead of a type 5 LSA. Flooded only within its area of origin; concerted to type 5 LSA on an ABR towards other areas.

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