Getting and Using IP addresses in Ansible Playbooks

An example playbook describing how you can fetch the IP addresses of different ansible managed hosts, using Ansible itself, and then use it in subsequent Ansible plays.

The script that I ran:
- name: Set Cluster variables
hosts: cluster
tasks:
cluster_ips: []

cluster_ips: "{{ cluster_ips + [ hostvars[item]['ansible_default_ipv4']['address'] ] }}"
with_items: "{{ groups['cluster'] }}"
run_once: true

cluster_names: "{{ groups['cluster'] }}"
run_once: true

# Variables for cluster set in the above three plays

- name: Print Variables
hosts: cluster
become: yes
run_once: true

tasks:

- name: Add UFW Rules
hosts: cluster
become: yes

tasks:
name: ufw
state: present

rule: allow
name: OpenSSH

rule: allow
src: '{{ item }}'
with_items: '{{ cluster_ips }}'

state: enabled

With Inventory
[cluster]
node-00
node-01
node-02

This example should scale to any number of nodes. Although Ansible itself will get significantly slower because the number of rules would increase non-linearly (O(n^2))