Exam ANS-C00 topic 1 question 108 discussion

D. As LexyA has already pointed out, Fn::Cidr only splits a CIDR into subnets, it does not check if the subnets are already in use or not. In order to be able to repeat the process, some kind of solution for keeping track of which subnets are in use and which are available is required. Thus, D is the best answer. The links mentioned in the comments also states that Fn::Cidr only splits a CIDR into subnets, without checking if the subnets are in use or not, which in this case is not good enough.

C. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-cidr.html

D. AWS Lambda and Amazon DynamoDB are required to manage available cidrs in a automatic way.

D - as only anwser that maintains a list of subnets to be referenced to ensure they are not in use.

My take is C. The fn::Cidr function does not select an available record by itself, but it´is necessary to create the networks. In my opinion you can play with fn::Cidr function and put some variables in the Ipblock field

The keyword is "available". There are actually two requirments in the question. First, find out CIDR ranges to decide which ranges are available. Second, use the available ranges in the CloudFormation. If the question only asks you to use the range, it won't mention available. C just uses the CIDR range. D is to find out the CIDR range first, then uses available CIDR range. My take is C.

C - can be the answer but question is to find out the available CIDRs, for which custom logic is needed and returned. Hence, Ans is D

It's definitely D. Because, we wanted to ensure Developers can use CF to deploy the resource in Subnets. Not selecting CIDR range by themselves. Option C. will let Developer to choose the CIDR range. No guarantee whether its available or not Option D. is correct. This will help Developers to automatically choose the Subnet CIDR ranges and when you delete lambda can release CIDR ranges back to DynamoDB table.

Agree with D. Not sure you guys understand the question.

D is the answer

My answer is C with D being a plausible solution.. https://aws.amazon.com/blogs/apn/amazon-vpc-for-on-premises-network-engineers-part-two/

Yeah is C

The developers have to create the subnets using available CIDR ranges thus the answer is C. Fn:Cidr function can be used in the cloudformation template to create subnets.

C - https://medium.com/@yaofei/aws-cidr-using-cloudformation-and-terraform-4f10bd86dbca

Correct answer is C

My take is C

D D D D D D