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  1. system says:

    Great job,your example are very smooth to learn .

  2. system says:

    very concise exlanation! :slight_smile:

  3. Hi Mohammed,

    Glad to hear you like it!

    Rene

  4. Hello sims.

    On Rene's example, he shows the output of the command show ip ospf database for R3. Here it is below as well:

    R3#show ip ospf database | begin Summary
    		Summary Net Link States (Area 1)
    
    Link ID         ADV Router      Age         Seq#       Checksum
    1.1.1.1         2.2.2.2         149         0x80000001 0x0033FB
    192.168.12.0    2.2.2.2         195         0x80000001 0x00219D
    
    		Summary ASB Link States (Area 1)
    
    Link ID         ADV Router      Age         Seq#       Checksum
    1.1.1.1         2.2.2.2         62          0x80000001 0x004DB9
    
    		Type-5 AS External Link States
    
    Link ID         ADV Router      Age         Seq#       Checksum Tag
    11.11.11.0      1.1.1.1         68          0x80000001 0x000F44 0

    In the above output, the Summary ASB Link States (Area 1) section displays the LSA type 4. A type for LSA has been received from 2.2.2.2 which is R2, which is indeed an ABR. With my last statement in the previous message, I wanted to confirm to you that type 4 LSAs come from ABRs, and R2 with an ID of 2.2.2.2 is indeed an ABR.

    If you have created a topology of your own and you cannot see any type 4 LSAs on R3, check to make sure the neighbour relationships are being created correctly between routers and make sure that R2 is indeed an ABR, that is, it should have at least one interface in each OSPF area you have created.

    I hope this has been helpful!

    Laz

  5. Hi Laz,

    For the below output, T3 and T4 LSA looks exactly the same (I have marked with arrow below) Therefore if we don't have T4 LSA, R3 should be able to find R1 with the help of T3 LSA?

    R3#show ip ospf database | begin Summary
    		Summary Net Link States (Area 1)
    
    Link ID         ADV Router      Age         Seq#       Checksum
    1.1.1.1         2.2.2.2         149         0x80000001 0x0033FB <<<<<<<<<
    192.168.12.0    2.2.2.2         195         0x80000001 0x00219D
    
    		Summary ASB Link States (Area 1)
    
    Link ID         ADV Router      Age         Seq#       Checksum
    1.1.1.1         2.2.2.2         62          0x80000001 0x004DB9  <<<<<<<
    
    		Type-5 AS External Link States
    
    Link ID         ADV Router      Age         Seq#       Checksum Tag
    11.11.11.0      1.1.1.1         68          0x80000001 0x000F44 0

    Best Regards,
    Neeraj

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