Posted on 2004-11-20
Last Modified: 2010-04-10
what is the different be taween  and and
Question by:teera
    LVL 23

    Assisted Solution

    by:adilkhan  = 254 Computers  = 3 Computers

    Author Comment

    Hi adilkhan
    How do you known 254 computer or 3 computer
    LVL 95

    Assisted Solution

    by:Lee W, MVP
    It's based on the bits. is equal to 11111111.11111111.11111111.00000000 (in binary).  It defines the network.

    For a clearer, more detailed explanation, you might want to have a look at these links:
    LVL 11

    Accepted Solution

    here we go ...

    consider you want 10 subnetworks.
    2^2 = 4 (4 - 2 = 2 => 2 usable subnetworks; you will always have two reserved network addrs: the broadcast addr and the network addr)
    2^3 = 8 (8 - 2 = 6 => 6 usable subnetworks)
    2^4 = 16 (16 - 2 = 14 => 14 subnetworks - this is what u want)

    Therefore you will have to use 4 bits for the netowrk addr
    what this means is that your network mask will be something like:

    1. 255.[1111 0000].0.0 = (if you are subnetting a class A addr) / here u will have 20 bits for hosts (2^20 - 2 hosts / per subnet)
    2. 255.255.[1111 0000].0 = (if you are subnetting a class B addr) / here u have 12 bits for hosts
    3. 25.255.255.[1111 0000]  = (in case you are subnetting a class C addr) / here u have 4 bits for hosts

    This is it! Basically!!!

    On some configurations you might be able to use what is called the "subnet zero" subnetwork which for a cisco router is configured using the "ip subnet zero" command. ... but this is another "area" ...


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