Ansible Iterate a Subnet

Ansible logic constructs are very simple. There are no for loops, but there is with_sequence. If we can make a list, we can iterate the list. This shows how to make a simple list of host addresses given a subnet (in CIDR notation).

- hosts: localhost
  gather_facts: no
    - name: Prime the list of hosts
        iter_hosts: []
    - name: Make list of hosts in subnet
      no_log: true #It's a lot of unnecessary chatter.
      # Start at 1 (with_sequence default) and
      # stop at size-2 to avoid network and broadcast addresses.
      with_sequence: end={{subnet|ipaddr('size')|int -2}}
        iter_hosts: "{{ iter_hosts + [subnet|ipaddr(item)|ipaddr('address')] }}"
    - debug: var=iter_hosts

With the list of hosts, ansible can try different things. It's a way to walk a LAN for discovery and testing, all within ansible.