How to get existing VPC cidr inside cloudformation stack

1
votes

creating cloudformation stack, which create additional subnet in vpc, i get VPCId (existing VPC) as parameter to stack. How to get VPC cidr inside CF stack

1
amazon-web-servicesamazon-cloudformation
For how to set and use parameters, see docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/… – jarmod

1 Answers

4
votes

From AWS::EC2::VPC - AWS CloudFormation:

Fn::GetAtt returns a value for a specified attribute of this type. The following are the available attributes and sample return values:

CidrBlock: The set of IP addresses for the VPC. For example, 10.0.0.0/16.

However, I suspect this only works on a VPC that was created within the CloudFormation template.

Since you want to refer to an existing VPC, you will need to write a CloudFormation custom resource using AWS Lambda.

It's a bit tricky, but there are some good sample templates at: stelligent/cloudformation-custom-resources