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Forum Replies

  1. Hi Rene,

    Question- does the subnet mask dictate the class of the network or the value of the octets? It seems here in this example that the subnet mask would dictate whether it was class A, B or C. However I was recently advised that it is not the subnet mask for example it has been recently stated to me:

    The class of a network is not determined by its subnet mask. The default subnet mask is determined by the class of a network. The class of a network is determined by the first octet of the IP.

    0-127 is considered “class A”.
    128-191 is considered “class B”.

    ... Continue reading in our forum

  2. James,
    Only the first four bits (3 really, since E class isn’t used) in the first octet determine class (as shown in the table below). You are correct in your example about

    Keep in mind, however, that “class” doesn’t really mean anything anymore. This is an outdated term that nobody really uses now. Even Cisco has stopped bothering to test on it!

    Binary (first 4 bits) Class
    0000                   A
    1000                   B
    1100                   C
    1110                   D
    1111                   E

  3. Zaman,
    These can be easily confused–in fact I had to review them myself to make sure I am giving you accurate information.

    VLSM is aptly named, because it means using a subnet mask of variable lengths throughout your organization with the same network block. For example, suppose your ISP has given you as an IP range. Without VLSM, you would have to pick a certain subnet mask, say, (/28) and stick with that. So if you wanted to use this block throughout your company, you would always have to use /28. This becomes wasteful in the

    ... Continue reading in our forum

  4. Here my summary:

    • /8 (8 bits Network, 24 bits Hosts = 2^24 = 256256256 = 16.777.216-2)
    • /9 (8+1 = 9 bits Network, 23 bits Hosts = 2^23 = 128256256 = 8.388.608-2)
    • /10 (8+2 = 10 bits Network, 22 bits Hosts = 2^22 = 64256256 = 2.097.152-2)
    • /11 (8+3 = 11 bits Network, 21 bits Hosts = 2^21 = 32256256 = 2.097.152-2)
    • /12 (8+4 = 12 bits Network, 20 bits Hosts = 2^20 = 16256256 = 1.048.576-2)

    ... Continue reading in our forum

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