- why /24 ? instead of 192.168.10/# notation query

Discussion in 'Server Networking' started by Scott, Oct 15, 2008.

  1. Scott

    Scott Guest

    Please note the query below is about a LABEL in an ALPHANUMERIC field which
    could contain anything but its the example of a notation i dont understand.

    1Im looking at a hardware firewall to understand the layout of the rules.
    One of the destinations shows the address "name" field as:

    ("name" field is alpha numeric and is just a label).

    When i EDIT the NAME that hold the rule for the address, the actual numeric
    address is displayed as:

    I understand subnet allows 256 IPs.

    So what im trying to get my head around is why "name" the destination as when i actaully edit the addrees its actually

    I understand this means allowing packet traffic incoming to 192.168.10.#.

    But why name it "" ?

    Why not name it "192.168.10.#"

    I see this with several ISPs i use, they tend to add "IP/ number". Dont
    understand the /number notation means. Can someone explain ?

    Thank you.
    Scott, Oct 15, 2008
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  2. Scott

    Chris M Guest

    The /24 is the number of 'on' bits in the subnet mask., represented as octets in binary is:


    Count the 1's :)
    Chris M, Oct 15, 2008
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  3. Scott

    JohnB Guest

    JohnB, Oct 15, 2008
  4. Scott

    Scott Guest

    The /24 is the number of 'on' bits in the subnet mask.

    Understood, simple now you mentiond it. So: / 24

    simply means:

    192.168.10.# / on subnet / meaning 256 IP available on the

    Its just another way to display without writing it !

    Thanks for the explaination guys :)
    Scott, Oct 16, 2008
  5. Scott

    Scott Guest

    thanks for the link too John.
    Scott, Oct 16, 2008
  6. Scott

    Chris M Guest

    No probs. While we're talking about it, remember that there won't be 256
    usable addresses: is the network ID is the subnet broadcast address
    Chris M, Oct 17, 2008
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