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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. 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!

    Laz

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

    br//zaman

  4. hI,

    Finally we can see 3.3.3.0 on R1. But that is E2 route type right ?
    E2 means that came from type 5. How Type 5 pass through R2 which is NSSA ?

    R1#show ip route ospf 
         3.0.0.0/24 is subnetted, 1 subnets
    O E2    3.3.3.0 [110/20] via 192.168.12.2, 00:07:25, FastEthernet0/0
    O IA 192.168.23.0/24 [110/2] via 192.168.12.2, 00:07:41, FastEthernet0/0
    

    ===================================================
    I think R3 will create Type 7 request and R2 will convert back to Type 5. So R1 can update 3.3.3.0/24 route as E2 :slight_smile:

  5. Hi Ravi,

    There is a good reason for this. With a stub or totally stub area, there is only one way out of the area and that’s the ABR.

    With an NSSA area, your ASBR could also advertise a default route.

    Now imagine both your ABR and ASBR advertise a default route. Which of the two default routes are used then? OSPF prefers routes in this order:

    * Intra area
    * Inter area
    * External
    * NSSA external

    So if the ABR would advertise a default route by default, then the default route from the ASBR would never be used. That’s why it is not enabled by default.

    Hope this helps!

    Rene

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