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Forum Replies

  1. system says:

    Hi Renee
    "There are a couple of things that you need to be aware of:
    No Automatic neighbor discovery so you need to configure OSPF neighbors yourself!
    No DR/BDR election since OSPF sees the network as a collection of point-to-point links.
    Only a single IP subnet is used in the topology above."
    Seems to me I have to commit them to memory.
    I have to say them out loud day in and day out like a mantra.
    I am asking whether or not there is a rhyme or reason to help me memorize or understand them.
    In case of PMNB (point to multipoint nonbroadcast) DLCI’s are not configured?

  2. Hi Lee,

    I don’t have a rhyme but there’s some logic to these OSPF network types:

    Only broadcast and non-broadcast require a DR/BDR election since OSPF sees these network types as “multi-access”. Everything with “point” in it is seen as a collection of point-to-point links so there is no DR/BDR election.

    Everything with “non-broadcast” requires you to configure neighbors since OSPF won’t be able to find them by itself.

    Only with point-to-point we use a subnet for each PVC, all other OSPF network types usually have a single IP subnet.

    Still some memorization to do but if you understand the logic, it will be easier to remember :slight_smile:

    Configuring DLCIs doesn’t have anything to do with OSPF or its network types but when you configure frame-relay, you always need DLCIs…maybe you get one from the frame-relay switch or you have to do it yourself.


  3. Hi Rene,

    Nice article.

    But OSPF network types are still a confusing topic after going through your articles. Is it possible to simplify things with a single post where you can update the differences and purpose of different network types. ?

  4. Thank You Rene, Your tutorial on Broadcast, Non-broadcast, Multi point are Brilliant.

    Now I am able to Discern.


  5. so I recreated this topology in GNS3 to see WireShark capture of OSPF messages, I could not get it to work because you did not specify “no shutdown” commands for s0/0 in the configuration section of your post.

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