Creating two resources in CF stack of VPCGatewayAttachment with same vpc-id and gateway-id fails

Question

Below is the template used to create CF stack:

Resources:

**InetGwAttachment**:

Properties:
      InternetGatewayId: !Ref 'InternetGateway'
      VpcId: !Ref 'CustomerVpc'
    Type: AWS::EC2::VPCGatewayAttachment

**InternetGateway**:

Properties:
      Tags:
        - Key: Name
          Value: !Join
            - ' '
            - - FS
              - !Ref 'OrgId'
        - Key: OrgId
          Value: !Ref 'OrgId'
    Type: AWS::EC2::InternetGateway

**NatAttachment**:

Properties:
      InternetGatewayId: !Ref 'InternetGateway'
      VpcId: !Ref 'CustomerVpc'
    Type: AWS::EC2::VPCGatewayAttachment

Getting create NatAttachment failed
vpc-123343434xxx|IGW already exists in stack arn:aws:cloudformation:us-west-2:1234xxx:stack/OrgId-xxxxxxx/a7d61140-3628-11ee-xxxx

Earlier this used to work. Have started seeing this recently.

Answer

I see in your template, you are trying to attach IGW at two places without any difference in those two bloacks.

Two resources **InetGwAttachment** and **NatAttachment** of same resource type **AWS::EC2::VPCGatewayAttachment**. If you compare these two blocks **InetGwAttachment** and **NatAttachment**, there is no difference at all and **NatAttachment** block is duplicate, which is why you are getting this error.

Am I missing something here, within same stack, if you'll attempt to duplicate the action, it'll error out with the message like "Resource already exist". Can you add complete template here.

If I am not getting it right, please mention here in comment section, I'd certainly dig further and assist you.

Abhishek

Creating two resources in CF stack of VPCGatewayAttachment with same vpc-id and gateway-id fails

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