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Example Microsoft Subnet Question

Discussion in 'Networks' started by miff2009, May 14, 2009.

  1. miff2009

    miff2009 New Member

    Hi All,

    I've been reading up on Subnetting and applied what I learnt to the following Microsoft exam example but I don't know how they derived the Network Addresses, may be someone can offer a better explanation. Thanks.


    Your boss asked you to subnet a network in the lab for an upcoming class. He hands you a piece of paper while he's on the phone and it simply says "192.168.10.x/25. 4 subnets." What is the subnet mask and the first address in each subnet?

    Correct Answer: /,,,

    (I got the answer right, based on the subnet - as it was the only one that had 128 in the answer, however, I didn't get the Network Addresses correct)

    Explanation given:

    Using the network notation /25 indicates you need to use 25 network bits. typically is used for the default subnet mask for Class C networks and uses 24 bits (often noted /24). Therefore, if you add one bit, you change the left-most bit in the right-most octet to 1. This equals 128, creating a subnet mask of The starting addresses (the first assignable IP address) in each subnet would have the right-most octet set to 1, 33, 65, and 97. The network addresses themselves would be,,, and

    I don't understand how they derived the number of Hosts, and it's making the assumption that the first network is

    I read the following site on Subnetting and used the same principles but didn't get it right. http://www.pantz.org/software/tcpip/subnetchart.html
  2. danielno8

    danielno8 Gigabyte Poster

    that subnet mask with gives you:>127 (host range 1-126)>255 (host range 129-254)

    To get the First host addresses given as the correct answer you would need a subnet mask of /27 or not /25
    Certifications: CCENT, CCNA

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