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  1. Hi Rene,
    Hope you are doing well :slight_smile:
    My question is, In ospf database/Topology table we find type-1 LSA,on that it shows Link ID and ADV. Router ID both are same why ??


  2. Hi Rene,
    I want to know how OSPF Prevent Inter-Area Loop at ABR and ASBR end ?? How its works if two ABR /ASBR Scenario ? How ABR do function ? I think a details write up needed regarding looping prevention issue in your clear text . Appreciate your write up on it .Thx


  3. Hello Mohammad

    The ADV Router ID heading shows the router ID of the advertising router, that is the router from which this LSA was received.

    Now the Link State ID heading is a little more tricky. According to the OSPF RFC, when a router is packaging all of its local, Type-1 Router LSAs into a single OSPF packet, and adds an LSA Header to the front of those LSAs, the “Link State ID” field in that header is always the Router-id of that router. Now…within each, individual LSA there is another field called the “Link ID” field. For each Router LSA it is THIS field that is under the Link State ID heading. This value may change depending on whether that Router LSA is describing a transit network, stub network, point-to-point network, or virtual-link.

    Now in the examples given by Rene, these are the same because the Router ID happens to be the loopback interface which also happens to be used as the ID for the specific link. THis is why they are the same, however, this is not always the case. This is especially true when you configure a router ID using the router-id x.x.x.x command in the OSPF configuration.

    I hope this has been helpful!


  4. Hi Laz,
    Thanks for your valuable reply on complex issue as always :slight_smile:
    Could you please reply on Looping issue for the intermediate time ?? It will very much helpful to keep my study continue .Many thanks


  5. Hi Laz ,
    Thans dear :slight_smile:
    I have read the doc before but some issue still confusing .Could you please give me clear concept of ABR,ASBR JOB while injecting LSA-3 & LSA-5 to other Area . Actually a bit confusion for two ABR , ASBR scenario . Could you please help me on two ABR,ASBR scenario .Many Thx


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