Preset Mapping of VPC Standards

[fozzy77]

I though this might be an option to introduce, rather than fixing the CIDR mask , it being built dynamically to encompass the use of mapping , do you think this would be of any benefit. This seems to work as expected on a local test

Mappings:
EnvMap:
Small:
subnetbits: "5"
cidrsize: "23"
Medium:
subnetbits: "6"
cidrsize: "22"
Large:
subnetbits: "7"
cidrsize: "21"

By removing the CIDR from parameters and replace with
Size:
Type: String
Description: Enter Small,Medium or Large
AllowedValues:
- Small
- Medium
- Large

Subnets to utilise something like
PrivateSubnet1:
Type: AWS::EC2::Subnet
Properties:
VpcId: !Ref VPC
AvailabilityZone: !Select [ 0, !GetAZs '' ]
CidrBlock: !Select
- 0
- Fn::Cidr:
- !GetAtt AllocateCidr.cidr
- 9
- !FindInMap [EnvMap, !Ref Size, subnetbits]
MapPublicIpOnLaunch: false
Tags:
- Key: Name
Value: !Sub ${Environment} Private Subnet (AZ1)