Thread: IP address range matching

  1. #1
    & the hat of GPL slaying Thantos's Avatar
    Join Date
    Sep 2001

    IP address range matching

    Running into this at work. I have IP address ranges like and I'm trying to figure out how that matches

    I thought the 0/17 only affected the last octet but it appears I'm wrong (via other documents) but even then I can't see how the 3rd octet matches.

    Any one have some references they could point me to?

  2. #2
    and the Hat of Guessing tabstop's Avatar
    Join Date
    Nov 2007
    The /17 means that only the first seventeen bits are used for the subnet mask -- which means, in the third octet, only the first byte must be matched. Your subnet goes from to

    You can probably google "subnetting calculator" or something like that.

    (Edit: first byte!?! first bit. Sorry.)
    Last edited by tabstop; 07-16-2009 at 04:30 PM.

  3. #3
    & the hat of GPL slaying Thantos's Avatar
    Join Date
    Sep 2001
    Got to love how just a little bit more searching after asking finds you the solution

    Turns out the IP is in CIDR notation - Wikipedia, the free encyclopedia where the /17 specifies the subnet mask.

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