Valid networks in a /25
0, 128
Valid networks in a /26
0, 64, 128, 192
Valid networks in a /27
0, 32, 64, 96, 128, 160, 192, 224
Valid networks in a /28
0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240
So......
1. 199.205.15.64/25 <Nope>
2. 199.205.15.8/27 <Nope>
3. 199.205.15.130/26 <Nope>
4. 199.205.15.192/26 <Yep>
5. 199.205.15.40/28 <Nope>
6. 199.205.15.96/26 <Nope>
I'd say you're right!
"Corrado Labinaz" <> wrote in message
news:...
> Hi to everyone,
> following a question from a 70-291 study exam, with the suggested correct
> responses.
> I belive these responses are wrong.
> First take a look at the question:
>
> ----------------------------
> Your organization has leased the Class C network 199.205.15.0/24. You are
> subnetting this network
> using VLSM. Your routers support the zero subnet and the longest match
> algorithm. You ask one of
> your support staff to design a subnetting structure, but when she submits
> this you suspect that some
> of the network/subnet mask allocations are invalid. Which of the following
> are not valid networks?
> (Choose all that apply).
>
> 1. 199.205.15.64/25 <Correct>
> 2. 199.205.15.8/27 <Correct>
> 3. 199.205.15.130/26 <Correct>
> 4. 199.205.15.192/26
> 5. 199.205.15.40/28
> 6. 199.205.15.96/26
> ----------------------------
>
> AFAIK, looking at the last octet of the above addresses and masks,
> 199.205.15.64/25 equate to
> 01000000 address
> 10000000 mask.
> This mean not all host bits are set to 0, so this is not a valid network.
> The same goes for:
> 199.205.15.8/27
> 199.205.15.130/26
> 199.205.15.40/28
> 199.205.15.96/26
>
> The only valid network is 99.205.15.192/26.
>
> What do you think?
>
> Kind regards,
> Corrado
>
>
>
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