How can I reference the Default VPC in CloudFormation?

Question

I have a stack which needs resources which need to be deployed in a certain VPC. I want to use the default VPC but I don't want to parameterize this. Is there a way to automatically obtain the default VPC value? (Like for example Fn::GetAZs: region for AZ's in a region).

Answer 1

The ID of the default VPC can be obtained using the following AWS CLI command:

$ aws ec2 describe-vpcs \
    --filters Name=isDefault,Values=true \
    --query 'Vpcs[*].VpcId' \
    --output text

vpc-a1b2c3d4

The above command will output something like: vpc-a1b2c3d4

You can assign this output to a variable and then pass it to your CF template like this:

$ default_vpc_id=$(aws ec2 describe-vpcs \
    --filters Name=isDefault,Values=true \
    --query 'Vpcs[*].VpcId' \
    --output text)

$ echo ${default_vpc_id}

vpc-a1b2c3d4