Discover IPv4 management address

discover_mgmt_ipv4_address.play.yml

# requires python-netaddr on the control vm
#   pip install netaddr

- name: Discover management ipv4 address
  hosts: localhost
  vars:
    mgmt_network_cidr: '172.19.0.0/16'  # Change this to reflect our mgmt. subnet cidr

  tasks:
  - name: Collect subnet addresses
    set_fact:
      ipv4_subnets:
        "{{ (ipv4_subnets | default([])) + [{

          'subnet':
            ( hostvars[inventory_hostname]['ansible_' ~ item]['ipv4']['address']
              ~ '/' ~
              hostvars[inventory_hostname]['ansible_' ~ item]['ipv4']['netmask']
            ) | ipaddr('subnet'),

          'ipv4':
            hostvars[inventory_hostname]['ansible_' ~ item]['ipv4']['address']

          }]
         }}"
    when:
        "{{ hostvars[inventory_hostname]['ansible_' ~ item]['ipv4'] is defined }}"
    with_items:
      - "{{ ansible_interfaces | map('replace', '-','_') | list }}"
    tags:
      - debug

  - name: Extract management ipv4 address
    set_fact:
      mgmt_ipv4_address:
        '{{ mgmt_ipv4 | selectattr("subnet", "equalto", mgmt_network_cidr) | map(attribute="ipv4") | first }}'

  - name: Echo mgmt_ipv4_address
    debug:
      msg: 'mgmt_ipv4_address is {{ mgmt_ipv4_address }}'