A user has created a VPC with CIDR 20.0.0.0/24. The user has created a public subnet with CIDR 20.0.0.0/25.
The user is trying to create the private subnet with CIDR 20.0.0.128/25. Which of the below mentioned
statements is true in this scenario?
A.
It will not allow the user to create the private subnet due to a CIDR overlap
B.
It will allow the user to create a private subnet with CIDR as 20.0.0.128/25
C.
This statement is wrong as AWS does not allow CIDR 20.0.0.0/25
D.
It will not allow the user to create a private subnet due to a wrong CIDR range
Explanation:
When the user creates a subnet in VPC, he specifies the CIDR block for the subnet. The CIDR block of a subnet
can be the same as the CIDR block for the VPC (for a single subnet in the VPC., or a subset (to enable multiple
subnets.. If the user creates more than one subnet in a VPC, the CIDR blocks of the subnets must not overlap.
Thus, in this case the user has created a VPC with the CIDR block 20.0.0.0/24, which supports 256 IP addresses
(20.0.0.0 to 20.0.0.255.. The user can break this CIDR block into two subnets, each supporting 128 IP
addresses. One subnet uses the CIDR block 20.0.0.0/25 (for addresses 20.0.0.0 – 20.0.0.127. and the other uses
the CIDR block 20.0.0.128/25 (for addresses 20.0.0.128 – 20.0.0.255..
A.
It will not allow the user to create the private subnet due to a CIDR overlap
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B is correct.
One subnet uses the CIDR block 20.0.0.0/25 (for addresses 20.0.0.0 – 20.0.0.127) and the other uses the CIDR block 20.0.0.128/25 (for addresses 20.0.0.128 – 20.0.0.255)
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B
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Sorry Chef, this time you are wrong.
The public IP address range should not be used as a private subnet.
B
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One subnet uses the CIDR block 20.0.0.0/25 (for addresses 20.0.0.0 – 20.0.0.127) and the other uses the CIDR block 20.0.0.128/25 (for addresses 20.0.0.128 – 20.0.0.255)
Agree, B is correct.
In fact, both subnet will be created.
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B
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B is right, no overlap here
http://www.subnet-calculator.com/
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B
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Just replicated this requirement and unfortunately, it does allow to create a subnet with CIDR 20.0.0.0/25. I also run a new instance to see what IP it get and it is 20.0.0.54, not after 0.129 as the answer B says: “create a private subnet with CIDR as 20.0.0.128/25”.
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B
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