Tasks to find the default VPC and its subnets

ec-vpc-tasks.yml

- name: Find default VPC for region
  command: "aws ec2 describe-vpcs --region={{ region }} --output=json --filters=Name=isDefault,Values=true --query=Vpcs[0].VpcId"
  register: default_vpc

- name: Set default_vpc_id fact
  set_fact:
    default_vpc_id: "{{ default_vpc.stdout | from_json }}"

- name: Find availability zones in the default VPC
  ec2_vpc_subnet_facts:
    region: "{{ region }}"
    filters:
      defaultForAz: "true"
      state: "available"
      vpc-id: "{{ default_vpc_id }}"
  register: default_subnets
  
 - name: Set subnet_ids fact
   set_fact:
     subnet_ids: "{{ default_subnets.subnets | map(attribute='id') | list }}"