AWS CloudFormation error with Security Groups and Network Interfaces, Invalid Parameter Combination

Question

I get this error whenever I launch my stack (Network interfaces and an instance-level security groups may not be specified on the same request) and cannot figure out what the issue is, even after changes and looking at the issue online.

My stack includes 2 ec2-instances in the public subnet, and 2 ec2-instances in the private subnet. The webservers(public) both have elastic ips, and have an individual security group for each.

I tried swapping SecurityGroupIds to SecurityGroups but that didn't change the error. I also tried removing Groupset completely, same error occurs.

WebServerInstance:
    Type: 'AWS::EC2::Instance'
    Properties:
      UserData: !Base64 
        'Fn::Join':
          - ''
          - - WebEIP=
            - !Ref WebEIP
      ImageId: ami-d7576bc1
      InstanceType: t2.micro
      KeyName: !Ref KeyName
      NetworkInterfaces:
        - AssociatePublicIpAddress: 'true'
          DeleteOnTermination: 'true'
          DeviceIndex: '0'
          GroupSet:
            - !Ref PublicSecurityGroup
          PrivateIpAddress: 10.1.1.100
          SubnetId: !Ref PublicSubnetAZ1
      SecurityGroupIds:
        - !Ref PublicSecurityGroup

After launching this stack, most of the resources are created except when it reaches WebServerInstance1 and WebServerInstance2 (the ec2 instances in the public subnet) where the error is

Network interfaces and an instance-level security groups may not be specified on the same request (Service: AmazonEC2; Status Code: 400; Error Code: InvalidParameterCombination

Dirty SR Dirty SR · Accepted Answer · 2019-06-06T16:47:02

I have solved the issue. Basically both GroupSet and SecurityGroupIds are interfering with each other. Remove the SecurityGroupIds line completely and leave GroupSet the same, then this is solved.

AWS CloudFormation error with Security Groups and Network Interfaces, Invalid Parameter Combination

1 Answers