subnetting - RFC1878 - 000's & 111's

Discussion in 'Cisco' started by Phil Schuman, Jan 27, 2005.

  1. Phil Schuman

    Phil Schuman Guest

    I was putting together some subnetting tables,
    and posted a couple of other msgs about subnetting.

    One of the questions that came up,
    was how to handle the 000 and 111 subnets ?
    (the first and last subnets)

    I've found that RFC1878 says everything is ok now,
    but that RFC was written in December 1995.

    So - if we have some old cisco 2501's running,
    from 1997 with - version 11.3 -
    or even some other routers that were acquired, installed,
    and have been just plain running for years -
    How should we view the RFC1878 issue ?

    What about other networks out there ?
    How many are using the 000 and 111 subnets ?

    tnx - Phil -
    Phil Schuman, Jan 27, 2005
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  2. Hi Phil,

    | What about other networks out there ?
    | How many are using the 000 and 111 subnets ?

    we are using a lot of cisco based networks with subnets like 000.
    When we configure a subinterface with IP, we configure in
    global mode
    "ip subnet zero".

    Is that the tink you´d like to hear?


    Carsten Remien
    Remien, Carsten, Jan 27, 2005
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  3. No problems in using them generally now. There were only a few odd
    problems with a few things out there that have been all fixed now.
    I think Novell was the worst offender, earlier versions of Netware IP
    (ie. stuff that would work back on Netware 3.xx??) failed to work correctly.
    Maybe Novell Bordermanager as well. Some HP stuff.

    Most normal stuff never had any problem with all 0's and all 1's subnets.
    Yep. Haven't had to deal with any customer having any issues since the
    late '90s at least.
    Pretty much non issue. Just 'ip subnet-zero' on all routers, and away
    you go. Cisco has supported that for quite some time, long before 1997.
    Pretty much everyone that I've seen.
    Doug McIntyre, Jan 28, 2005
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