A national retail chain needs to design an IP addressing scheme to support a nationwide network. The company needs a minimum of 300 sub-networks and a maximum of 50 host addresses per subnet. Working with only one Class B address, which of the following subnet masks will support an appropriate addressing scheme? (Choose two.)
A.
255.255.255.0
B.
255.255.255.128
C.
255.255.252.0
D.
255.255.255.224
E.
255.255.255.192
F.
255.255.248.0
the correct answer should be C and F
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The correct answer is B and E
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We need to remember the default subnet mask of class B is 255.255.0.0. Next, the company requires a minimum of 300 sub-networks so we have to use at least 512 sub-networks (because 512 is the minimum power of 2 and greater than 300). Therefore we need to get 9 bits for network mask (29=512), leaving 7 bits for hosts which is 27-2 = 126 > 50 hosts per subnet.This scheme satisfies the requirement -> B is correct.
We can increase the sub-networks to 1024 ( 1024 = 210), leaving 6 bits for hosts that is 26= 64 > 50 hosts. This scheme satisfies the requirement, too -> E is correct.
Notice: The question asks “The company needs a minimum of 300 sub-networks and a maximum of 50 host addresses per subnet” but this is a typo, you should understand it as “”The company needs a minimum of 300 sub-networks and a minimum of 50 host addresses per subnet”.
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@ amy u are very crrect. the right ans is B and E
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B and E is correct
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yea the correct answer is B & E
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administrators, change the answers! they are not correct! the correct answers is B and E!!!
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nope. there is no correct answer.
remember – only one class b address.
lets take 172.16.0.0
The closest number to 50 hosts is 64. lets start:
300 networks * 64 hosts = 19200. The closest number is 32768 so it will be 255.255.128.0
go :
1 – 172.16.0.0
2 – 172.16.0.64
3 – 172.16.0.128
.
last – 172.16.74.192 .
so : 255.255.128.0 (must be 512 because 300 is more than 255. networks) and 255.255.255.192 (64 hosts).
It CANT be 255.255.255.128 – what is it ? 128 adresses of what ?
That is what i think 🙂
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i do’t understand
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B and E are correct. Look at it this way. Lets take the class B address as 172.16.0.0
/25 is 128 in 3rd octet as class B
172.16.0.0 – 172.16.0.127
172.16.0.128 – 172.16.0.255
172.16.1.0 – 172.16.0.127
172.16.1.128
See? Each subnet here can contain a MINIMUM 50 hosts (question is incorrect as person above mentioned)
And then you can borrow 1 more bit to make /26
172.16.0.0 – 172.16.0.63
172.16.0.64 – 172.16.0.127
172.16.0.128 – 172.16.0.191
172.16.1.192
In both you have a minimum of 300 subnets ans hosts.
Hope it helps.
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The correct answer is B and E, the question itself is really confusing, because it states 300 subnets minimum and 50 host maximum each network, from my understanding we can have more subnets, but not less than 300, and we can have 50 hosts, but not more than 50.
From my view “50 host maximum” should be replaced by “50 host minimum”
Please let me know if you are agree with me, maybe I misunderstood the question.
Thank you in advance.
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there is only one correct answer (E) and the other which suppose to be 255.255.128.0 instead of (B)255.255.255.128…..
we need 300sub-networks of 50 host maximum…… 50 is close to 64 host portion in sub-netting.
300×64=19200 hosts
Class B is in use so we need 19200/256 hosts per subnet= 75 sub-network of 256 host… which mean we need 128 to cover 75 subnetworks of 256 hosts.
we need to divide 256 host into group of 64 host …. we need to use the 4th octet… which will be .192
Answer 1: 255.255.128.0
Answer 2: 255.255.255.192
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i don’t understand :/
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it should have been “a minimum of 50 host addresses per subnet”
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