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  1. Hi Jason,

    These have to be match yes, otherwise no neighbor adjacency is established.


  2. Dear Rene,
    Could enabling BFD be better option than reducing dead-hello timers regarding the consuming router resource?
    Which method do you recommend ?

  3. Hi Mohammad,

    A good question. I am referring to you to RFC which is a type of publication from the Internet Engineering Task Force (IETF) and the Internet Society (ISOC), the principal technical development and standards-setting bodies for the Internet.
    On April 1998, they have created the publication RFC 2328 for OSPF version 2, and on point 9.5 they spoke about “Sending Hello Packets” as following:

    “Hello packets are sent out each functioning router interface. They are used to discover and maintain neighbor relationships.[6] On broadcast and NBMA networks, Hello Packetsare also used to elect the Designated Router and BackupDesignated Router.The format of an Hello packet is detailed in Section A.3.2. The Hello packet contains the router’s Router Priority (used in choosing the Designated Router), and the interval between Hello Packets sent out the interface (HelloInterval). The Hello Packet also indicates how often a neighbor must be heard from to remain active (RouterDeadInterval). Both HelloInterval and
    RouterDeadInterval must be the same for all routers attached to a common network. The Hello packet also contains the I
    P address mask of the attached network (Network Mask). On unnumbered point-to-point networks and on virtual links this field should be set to”

    In other word to say, this is how OSPF works as per Hello & Dead interval to form a neighbor-ship with another router… Additionally, to form neighbor-ship with another OSPF router, there is also other fields to be matched in addition of the hello/deal interval which are:
    - Area id
    - Authentication password
    - Stub area Flag

    All those are contained in the Hello packet sent from neighbor router(s) they must be matched. I really advise you to check this lesson where you can find more information about this topic:
    Introduction of OSPF

    Hope I could answer your question.

  4. sir
    1> you have this command ip ospf dead-interval minimal hello-multiplier 3 why you have used 3 what is the meaning of minimal hello-multiplier 3 , I understand that when we select minimal the =n our dead interval time will be 1 but why you used hello-multiplier 3 please explain it but if i am using 4 instead of 3 my neighbor adjancecy is working on R1 i have used hello-multiplier 3 and R2 i have used hello-multiplier 4 and they have neighbor adjancency please explain it

  5. Hello Bhai,

    The “3” in that command means how many hello packets will be sent in 1 second period. Also when you use that command, that is ip ospf dead-interval minimal hello-multiplier x; The x number or the number of hello packets sent per second doesn’t need to match between the two neighbors.

    The main important thing about this feature is for critical environment to be able to detect the loss of neighborship in 1 second.


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