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2012年3月27日

OSPF LSA type

LSA type 1 – Router LSAs are sent from a router to other routers in the same area. It contains information regarding the routers interfaces in the same area, relevant interfaces IPs, its adjacent routers on those interfaces and sub networks
LSA type 2 – Network LSAs are generated by the DR on a multi access segment, and provides similar information to an LSA type 1 for the multi access segment and subnet which it belongs
LSA type 3 – Network Summary LSAs are generated by ABRs and contain the subnets & costs but omit the topological data from all subnets in one area and sent to another area via the ABR
LSA type 4 -ASBR summary LSAs are from ASBRs and are identical in structure to a type 3 LSA and sent when crossing an AS boundary
LSA type 5 -Are AS external LSAs which are originated by ASBRs and describe external networks
LSA type 6 – Is defined as a Group Membership LSA but not used in Cisco devices
LSA type 7 -NSSA External LSAs are generated by the ASBR in an NSSA area
LSA type 8 – Is defined as a External Attribute LSA but not used in Cisco devices
LSA types 9 to 11 – Defined as Opaque LSAs and are reserved for future expansion

ref.: http://communitystring.com/2008/07/ospf-lsa-types/



Area Type Type 1 & 2 (within area) Type 3 (from other areas) Type 4 Type 5 Type 7
Standard & backbone Yes Yes Yes Yes No
Stub Yes Yes No No No
Totally stubby Yes No No No No
NSSA Yes Yes No No Yes
Totally stubby NSSA Yes No No No Yes




ref.: https://learningnetwork.cisco.com/docs/DOC-7924

OSPF - Normal, Stub, Totally Stub and NSSA Area Differences

ref.: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094aaa.shtml#definestub

NormalNone
StubNo Type 5 AS-external LSA allowed
Totally StubNo Type 3, 4 or 5 LSAs allowed except the default summary route
NSSANo Type 5 AS-external LSAs allowed, but Type 7 LSAs that convert to Type 5 at the NSSA ABR can traverse
NSSA Totally StubNo Type 3, 4 or 5 LSAs except the default summary route, but Type 7 LSAs that convert to Type 5 at the NSSA ABR are allowed

more information about LSA type: