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Forum Replies

  1. Hi Rene,

    Ok. Thanks :slight_smile:


  2. Hello Azeem!

    This is a very good question and indicates that you are thinking very deeply of the reasons behind specific functionalities of OSPF. Yes, it does make sense to assume that if there is no change to the network, then at the end of the sequence you describe, it should not need to go to Step A. However, it is important to realise the purpose of the sending of the LSA every 30 minutes in order to answer this question.

    When LSAs are sent because of a topology change, the sequence number is incremented. This indicates that the LSA contains newer inform

    ... Continue reading in our forum

  3. Hello Mohammad

    If we see one prefix in the database that is continuously changing the sequence number, then this means that for some reason, a route is flapping on the network. This is usually due to a routing loop that may occur not within an area, but via multipoint redistribution, that is, when a route is redistributed into another AS and then it is re-redistributed back into the original AS from another redistribution point. Solutions to such problems include route tagging which is explained further in this lesson:


    ... Continue reading in our forum

  4. Hi laz,

    Great explanation.


  5. Hello Naresh

    If you put these numbers into a Hex to Decimal converter, you’ll see that you end up with
    0x80000001 = 2147483649
    0x7FFFFFFF = 2147483647

    This looks strange. Actually, it looks completely incorrect!! The reason these numbers are used is because the LSA sequence numbers are signed. That is, they include a negative or positive sign which is indicated by the very first of the 32 bits. The LSA sequence numbers will start with 0x80000001 which is compared to binary below:

    Hex       0x8  0    0    0    0    0    0    1
    Binary    1000 0000 0000 000
    ... Continue reading in our forum

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