AWS Certified Solutions Architect – Professional — Question 121

Doug has created a VPC with CIDR 10.201.0.0/16 in his AWS account. In this VPC he has created a public subnet with CIDR block 10.201.31.0/24.
While launching a new EC2 from the console, he is not able to assign the private IP address 10.201.31.6 to this instance.
Which is the most likely reason for this issue?

Answer options

• A. Private address IP 10.201.31.6 is currently assigned to another interface
• B. Private IP address 10.201.31.6 is reserved by Amazon for IP networking purposes.
• C. Private IP address 10.201.31.6 is blocked via ACLs in Amazon infrastructure as a part of platform security.
• D. Private IP address 10.201.31.6 is not part of the associated subnet's IP address range.

Correct answer: A

Explanation

The correct answer is A because if the private IP address 10.201.31.6 is already in use by another interface, it cannot be assigned to a new EC2 instance. Option B is incorrect as AWS does not reserve this IP for networking purposes, and option C is not applicable since ACLs do not block specific IP assignments in this context. Option D is also wrong because 10.201.31.6 is indeed within the subnet's IP range.