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Forum Replies

  1. Rene just a question, why is that cisco never put a default route in NSSA? why did you need to configure it manually? does is have a reason why they didn’t put it in default?

  2. andrew says:

    The answer lies in the complexity of the network you are dealing with. In a lab / learning environment, you often see OSPF stub examples represented with just a single router connecting the stub area to the rest of the network. In real life, however, you might be dealing with multiple exit points out of the stub (note, this does not mean the stub is a transit area–by definition it can’t be). In this case, it might not be optimal to have all traffic leaving the stub area to flow through just one ABR. In order for routing decisions to be made as to which ABR should be used for a particular destination, it would be necessary to have type 3 LSAs. As you know, a Totally Stubby Area doesn’t allow Type 3 LSAs (other than the ABR generated default route).

    A similar argument can be made for NSSA vs NSSA Totally Stubby Area

  3. Hi Rene,
    I have a question , What is the significance of forward address in ospf ??? .


  4. Hello Mohammad

    A forwarding address in OSPF allows extra hops to be avoided in certain routing situations because it allows a router to specify another router’s IP address as the forwarding or next hop address address. So essentially, a R1 can tell R2 that the next hop router for a destination is R3.

    You can find a detailed description of forwarding addresses in OSPF and its uses at this Cisco documentation.

    I hope this has been helpful!


  5. Hi Laz,
    Now got the answer . Many Thanks


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