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  1. #1
    Join Date
    May 2009
    Location
    MUSCAT
    Posts
    72

    Default /25 can be used with classful addressing?

    Hi

    Can we configure the router with the ip address 151.78.1.1/25 in one of it's interface to use a classful routing protocol?


    Thanks

    S.Swaminathan

  2. #2
    Join Date
    Aug 2009
    Location
    California, US
    Posts
    115

    Default

    Yes you can...

    if you use a mask other than a classful mask, all router interfaces must be configured with the same mask. This is because the subnet mask is not sent in the routing updates so the only way the router would know about the /25 is by the config on the local interface.

  3. #3
    Join Date
    Jun 2009
    Location
    Denver, CO
    Posts
    226

    Default Classful Routing

    Quote Originally Posted by swaminathan View Post
    Hi

    Can we configure the router with the ip address 151.78.1.1/25 in one of it's interface to use a classful routing protocol?


    Thanks

    S.Swaminathan
    As Don said above, YES ... and no ...

    RIP does not support VLSM so the masks would need to be the same!
    RIPv2, EIGRP, and OSPF do support VLSM so you may use different masks.

    There are two issues one need keep in mind when dealing with routing/routing protocols in general.

    1.) Do the boundaries of the classful network overlap across the topology?
    2. Are the networks continuous of discontinuous?

    You need to understand which routing protocol supports what features, their limitations, and most importantly ... How to Expolit them to your advantage.


    no auto summary is your friend ... most of the time.
    John

    CCNA
    CCNA:Voice
    ATSA Internetworking - AdTran

  4. #4
    Join Date
    May 2009
    Location
    MUSCAT
    Posts
    72

    Default Cleared my doubt!

    Hi

    Thanks for all who replied

    Regards

    Swaminathan

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