You are adding a new spoke to the existing transit VPC environment using the AWS...

When using an AWS CloudFormation template to add a new spoke to an existing transit VPC environment, the necessary components are:

The BGPASN value used for the transit VPC (Option C): BGP Autonomous System Number (ASN) is required for setting up BGP routing between the transit VPC and the new spoke. This number uniquely identifies the system in BGP routing and is crucial for correct routing and avoiding routing conflicts.

The tag value of the spoke (Option D): Tags in AWS are used to identify and manage resources. The tag value assigned to a spoke VPC helps in organizing, managing, and locating the VPC within the larger AWS environment. Tags are essential for automation scripts and policies that depend on specific identifiers to apply configurations or rules.

References: AWS CloudFormation and AWS Transit Gateway documentation provide guidance on the use of BGPASN and tags for managing and automating VPC deployments effectively.