Understanding all the OSPF LSA types is one of the keys to understanding OSPF, so its definatly worth me making a few notes on them

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

11 thoughts on “OSPF LSA Types

  1. Ashish

    Very useful Information….I want’t to know also that we can do CCSP after CCNA. Can any company’s are working CCSP in INDIA or not.

  2. waqar

    Hi Bradly , thankyou for posting such usefull information it is very easy to be understood but i have little confusion in type 4 and type 5 lsa , thier job seems to be the same , is there any difference between them ?

    thanks in advance..

    1. Imran

      Hi Waqar

      LSA4 : is used to inform about the asbr . While LSA5 : is used to inform about the summary of external n/w .

  3. waqar

    i think the difference is type 4 lsa adviertises routes to other AS routers.
    and type 5 lsa advertises other AS routes into OSPF domain.

    am I correct

  4. Bipin

    Diff between lsa-4 & lsa-5 is that, Lsa’s generated by Asbr & forwarded to all ABR’s, & convert it into Lsa-3 while
    In lsa-5 is also generated by AsBR but it decribe the external network & flooded all over area as lsa type 5 only.
    e.g if redistribution is done at that time.


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