As an AWS consultant, you have been assigned to automate the VPC creation process. You successfully performed POC at the ap-northeast-1 region using AWS CloudFormation Template. With this template, you have created a VPC with public & private subnets with CIDR range along with an Internet Gateway. You need to replicate the same template in other regions for deployment. Which of the following can be used to incorporate the CIDR range of the region to the template so that users in each region can select these values?

Answer options:

A.Create Reference in AWS CloudFormation to allow users in different regions to specify region-specific CIDR ranges during Stack creation. 
B.Use Parameters in AWS CloudFormation to allow users in different regions to specify region-specific CIDR ranges during Stack creation.
C.Use Functions Fn::Cidrin AWS CloudFormation to allow users in different regions to specify region-specific CIDR ranges during Stack creation. 
D.Use Functions Fn::Select in AWS CloudFormation to allow users in different regions to specify region-specific CIDR ranges during Stack creation. 

Correct Answer – B
Template Parameters can be used to customize Resource Properties in a template so that these templates can be re-used in deployment in other regions. In the above case, with Template Parameters, users can specify the CIDR range of a specific region while creating a stack.
Option A is incorrect as Reference will return physical ID for the resources. This will be used to refer to parameter values in a template.
Option C is incorrect as Fn::Cidr can be used to create smaller CIR blocks for a specified count& size from a larger CIDR block. This cannot be used to specify the CDR range during Stack creation.
Option D is incorrect as Fn::Select can be used to select one value from a range of values in a function. This cannot be used to specify the CDR range during Stack creation.
For more information on using AWS CloudFormation Templates for VPC creation, refer to the following URL
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/parameters-section-structure.html