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13 Cards in this Set
- Front
- Back
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Type 1 LSA
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Router - Each router creates its own Type 1 LSA to represent itself for each area to which it connects. The LSDB for one area contains one Type 1 LSA per router per area, listing the RID and all interface IP addresses on that router that are in that area. Represents stub networks as well.
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Type 2 LSA
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Network - One per transit network. Created by the DR on the subnet, and represents the subnet and the router interfaces connected to the subnet.
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Type 3 LSA
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Net Summary - Created by ABRs to represent subnets listed in one area's Type 1 and 2 LSAs when being advertised into another area. Defines the links (subnets) in the origin area, and cost, but no topology data.
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Type 4 LSA
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ASBR Summary - Like a Type 3 LSA, except it advertises a host route used to reach an ASBR.
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Type 5 LSA
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AS External - Created by ASBRs for external routes injected into OSPF.
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Type 6 LSA
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Group Membership - Defined for MOSPF; not supported by Cisco IOS.
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Type 7 LSA
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NSSA External - Created by ASBRs inside an NSSA area, instead of a Type 5 LSA.
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Type 8 LSA
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External Attributes - Not implemented in Cisco routers.
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Type 9-11 LSA
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Opaque - Used as generic LSAs to allow for easy future extension of OSPF; for example, Type 10 has been adapted for MPLS traffic engineering.
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OSPF uses a DR in a subnet for two reasons:
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1 - To create and flood a Type 2 network LSA for that subnet
2 - To aid in the detailed process of database exchange over that subnet |
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Who gets to be DR?
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- router with the highest priority (default 1, max 255, set with ip ospf priority value interface subcommand)
- If tied on priority, choose the router with highest RID - Choose a BDR based on next best priority, or RID if there is a tie |
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Three ways to influence choice of best OSPF route:
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reference bandwidth, interface bandwidth, OSPF cost
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default OSPF cost equation
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(reference bandwidth)/(interface bandwidth)
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