AWS CloudFormation: Reference to subnet causing error

Question

I am trying to build an AWS CloudFormation template to create a VPC, public subnet, and then launch an EC2 instance into that subnet. While I'm able to create the VPC and subnet resources when I try to launch the EC2 instance into the newly created subnet I get an error:

The requested configuration is currently not supported. Please check the documentation for supported configurations. (Service: AmazonEC2; Status Code: 400; Error Code: Unsupported; Request ID: 953bf578-375e-4d4a-bc27-b7193543ea94)

If I comment out the reference to the subnet in the EC2 creation block, the script works but the instance gets launched into a default subnet and not the one created earlier in the script (which isn't what I want).

The script:

Resources:
  VPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'false'
      EnableDnsHostnames: 'false'
      InstanceTenancy: dedicated
  PublicSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.0.0/24
      AvailabilityZone: !Select [ 0, !GetAZs ]
  InternetGateway:
    Type: 'AWS::EC2::InternetGateway'
    DependsOn: VPC
  AttachGateway:
    Type: 'AWS::EC2::VPCGatewayAttachment'
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway
  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
  PublicRoute: 
    Type: 'AWS::EC2::Route'
    DependsOn: 'AttachGateway'
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
  PublicSubnetRouteTableAssociation:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    Properties:
      SubnetId: !Ref PublicSubnet
      RouteTableId: !Ref PublicRouteTable
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow http to client host
      VpcId: !Ref VPC
      SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
      - IpProtocol: tcp
        FromPort: 22
        ToPort: 22
        CidrIp: 0.0.0.0/0
  Ec2Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-0323c3dd2da7fb37d
      SubnetId: !Ref PublicSubnet  # The offending line (?)
      KeyName: MyEC2KeyPair

Chris Williams Chris Williams · Accepted Answer · 2020-05-22T16:59:48

This is a result of your VPC tenancy being dedicated.

I can confirm that t2 instances do not support dedicated hosts. Either remove dedicated hosting for the VPC or update your instance type to be something else.

You can update the VPC tenancy to default which will return with shared hosting, alternatively look at a T3 burstable instance which is supported.

Look here for additional information: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/dedicated-instance.html

AWS CloudFormation: Reference to subnet causing error

1 Answers