Reference an existing AWS VPC Id in CloudFormation script when creating subnets

Question

如何在CloudFormation脚本中引用现有VPC的VPC Id（之前已在单独的CloudFormation脚本中创建）以便在VPC中创建子网？

Answer 1

In the template defining the VPC, include the VPC ID in the outputs section:

"Outputs" : {
    "VPC" : {
        "Value" : {"Ref":"VPC"},
        "Description" : "VPC ID"
    },
    ...
}

In the template for the stack using the VPC, define a parameter for the VPC ID:

"Parameters" : {
    "VPC" : {
        "Type" : "String",
    },
    ...
}

When creating this stack, call describe-stack on the VPC-defining stack to get the ID from outputs, and pass it as the VPC parameter to create-stack .

Answer 2

Or get vpc id from input, such as

 "VpcId" : {
      "Type" : "AWS::EC2::VPC::Id",
      "Description" : "VpcId of your existing Virtual Private Cloud (VPC)",
      "ConstraintDescription" : "must be the VPC Id of an existing Virtual Private Cloud."
    },

Answer 3

Reference it by name ie. "VpcId" : { "Ref" : "myVPC" }, In something like:

    {
   "Type" : "AWS::EC2::Subnet",
   "Properties" : {
      "AvailabilityZone" : String,
      "CidrBlock" : String,
      "Tags" : [ Resource Tag, ... ],
      "VpcId" : { "Ref" : String }
      }
    }  

Documentation here: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-subnet.html