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  1. Junior Member
    Join Date
    Sep 2017
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    #1

    Default On exam questions pertaining to subnet masks, is classful addressing implied?

    On practice questions like these that I got from my class, when they have a 10 network, does that actually mean Class A address only, or could it be a Class B using (what was reserved for) the Class A address space? Since I thought nowadays there aren't really classful boundaries anymore and you can use different subnet masks with different addressing schemes

    The network administrator is asked to configure 113 point-to-point links. Which IP addressing scheme defines the address range and subnet mask that meet the requirement and waste the fewest subnet and host addresses? *


    10.10.0.0/16 subnetted with mask 255.255.255.252
    10.10.0.0/18 subnetted with mask 255.255.255.252
    10.10.1.0/24 subnetted with mask 255.255.255.252
    10.10.0.0/23 subnetted with mask 255.255.255.252
    10.10.1.0/25 subnetted with mask 255.255.255.252

    Correct answer
    10.10.0.0/23 subnetted with mask 255.255.255.252

    Question is a bit confusing, by the way, since the /notation and subnet masks are different. And these masks in a Class A network would mean tens of thousands of subnets with a few hundred hosts each... which makes me think the question could be referring to a B instead
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  2. Senior Member
    Join Date
    May 2013
    Posts
    1,472

    Certifications
    CISSP, CISA, GWAPT, GSEC
    #2
    Basically the question wants a separate network for each point-to-point connection...so each network will need 4 addresses (network, broadcast, and two nodes)...take 113 * 4 = 452 addresses needed. Class C (/24) will give you 256 addresses, subtract one bit (/23...256 * 2) and you will cover the addresses needed.

    I do see how the question is confusing because they provide you the subnet mask of what each network will actually use, but they also are asking you to pick the network that will have to be subnetted.

    Usually questions are pretty clear if they want a classful address.../8, /16, /24...just know the subnet masks / CIDR notation and the corresponding address ranges just incase.
    Last edited by TechGuru80; 04-08-2018 at 09:30 PM.
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