AWS Cloudformation nested Functions (Split, Select, Join, Ref)

Question

I’m encountering an error as ‘Value of property CidrBlock must be of type String’, while I’m trying to get the CIDR block set by using the user in the Parameters, split the CIDR by "." to get individual numbers and join CIDR[0], CIDR[1], "4.0/24". The following function is used:

"CidrBlock": {

                "Join": [

                    ".",

                    [

                        {

                            "Select": [

                                "0",

                                {

                                    "Split": [

                                        ".",

                                        {

                                            "Ref": "2CIDR"

                                        }

                                    ]

                                }

                            ]

                        },

                        {

                            "Select": [

                                "1",

                                {

                                    "Split": [

                                        ".",

                                        {

                                            "Ref": "2CIDR"

                                        }

                                    ]

                                }

                            ]

                        },

                        "16.0/24"

                    ]

                ]

            },

I need to build the CIDR of each subnet using the CIDR of VPC and also may I know the issue with the above function? Kindly suggest me with any solutions.

Answer 1

"Fn::Join" is the function and “Join” is not  a function. I guess this might be the reason causing you the issue.

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