Since we deploy a public and a private subnet, we want to create them into an Availability Zone that contains our target instances, in this case p4d. We consult their availability in the region we use (us-east-1) through the following AWS CLI command:
`aws ec2 describe-instance-type-offerings --location-type availability-zone \ --filters Name=instance-type,Values=p4d.24xlarge --region us-east-1 --output table`

We see three availability zones containing p4d instances, we pick one of them (`us-east-1c`, yours may be different) when deploying our network stack. This can be done with the AWS Console or the AWS CLI. In our case we use the latter as follows

`aws cloudformation create-stack --stack-name VPC-Large-Scale --capabilities CAPABILITY_IAM --template-body file://VPC-Large-Scale.yaml --parameters ParameterKey=SubnetsAZ,ParameterValue=us-east-1c`
