VLSM question

satishtechsatishtech Member Posts: 243
I did not understand this VLSM question from learncisco.net
is my explanation correct

Question: You are implementing a VLSM network. You are using the Class A network of and need to create networks that support 254 hosts that will be used for each LAN. The tenth network that was created will be used for addressing all the point-to-point links between routers at HQ, all the point-to-point WAN links, and any point-to-point links in the branch offices.

What is the subnet ID of the second point-to-point network created?

Correct answer: D

Explanation :

/20 is the mask
block size 16
10th subnet is
further subnetting this with a /30 mask
the second pt-to-pt network would be ...


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    clarsonclarson Member Posts: 903 ■■■■□□□□□□
    the networks support 254 hosts. that is a /24
    so 10th network is
    point to point networks are /30
    block size is 4
    second /30 network is
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    satishtechsatishtech Member Posts: 243
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    randell09randell09 Registered Users Posts: 3 ■□□□□□□□□□
    Hi Guys

    My Name is Randell and i am new to this. Can anyone please explain to me in more detail as i am confused right now. How does one get to the tenth subnet being

    I would appreciate your assistance.
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    randell09randell09 Registered Users Posts: 3 ■□□□□□□□□□
    my apologies . meant to say tenth subnet being
    and the second pt-to-pt network ?
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    clarsonclarson Member Posts: 903 ■■■■□□□□□□
    first of all the network your starting out with is /8
    each network needs to support 254 hosts. so you create /24 subnets for each network /24 is first network /24 is second /24 is thrid
    .... /24 is the ninth /24 is the 10th /24 subnet or you start counting from zero. So tenth network is 10 - 1 or 9

    the /24 network is going to used for pt to pt networks use a /30 and their block size is 4 /30 is the first pt to pt second is 0 + the block size (or 4) /30 is the second pt to pt
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    randell09randell09 Registered Users Posts: 3 ■□□□□□□□□□
    Hi Clarson

    Thank you for clearing that up. it makes more sense to me now. much appreciated
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