Network Automation with Red Hat Ansible Automation Platform

In previous versions, Ansible was unable to gather facts for managed network nodes using the default fact gathering method of setting the gather_facts keyword to true.

In Ansible version 2.9 and later, if you set the gather_facts keyword to true, then Ansible tries to detect the network platform and use the appropriate *_facts module to gather facts.

The default setting is to gather a minimal subset of facts. This is equivalent to setting the gather_subset parameter to min.

To view a minimal subset of facts for a specific network platform, create a short playbook with a play that gathers facts by setting the gather_facts keyword to true. Then use the ansible.builtin.debug module to display the value of the ansible_facts variable.

---
- name: Gather and display default facts for IOS managed nodes
  hosts: ios
  gather_facts: true
  tasks:
    - name: Display facts
      ansible.builtin.debug:
        var: ansible_facts

The following play gathers and displays the equivalent set of facts as the previous play:

---
- name: Gather and display default facts for IOS managed nodes
  hosts: ios
  gather_facts: false
  tasks:
    - name: Gather IOS facts
      cisco.ios.ios_facts:
        gather_subset:
          - min

    - name: Display facts
      ansible.builtin.debug:
        var: ansible_facts

Use *_facts resource modules to gather facts for your managed nodes. For example, for Cisco IOS or IOS XE managed nodes, use the cisco.ios.ios_facts resource module. For Juniper Junos managed nodes, use the junipernetworks.junos.junos_facts resource module.

View the collections documentation for each network platform at https://docs.ansible.com/ansible/latest/collections/ to determine which modules to use.

To view all available facts for a specific network platform, create a short playbook that gathers all facts by setting the gather_subset parameter to all. Then use the ansible.builtin.debug module to display the value of the ansible_facts variable.

---
- name: Gather and display all facts for IOS managed nodes
  hosts: ios
  gather_facts: false
  tasks:
    - name: Gather IOS facts
      cisco.ios.ios_facts:
         gather_subset:
            - all

    - name: Display facts
      ansible.builtin.debug:
        var: ansible_facts

When you run the playbook, the facts are displayed in the output:

[user@host ~]$ ansible-navigator run iosfacts.yml -m stdout

PLAY [Gather and display facts for IOS managed nodes] *************************

TASK [Gather IOS facts] **********************************************************
ok: [iosxe2.lab.example.com]
ok: [iosxe1.lab.example.com]

TASK [Display facts] *******************************************************
ok: [iosxe1.lab.example.com] => {
    "ansible_facts": {
        "net_all_ipv4_addresses": [
            "172.25.250.20"
        ],
        "net_all_ipv6_addresses": [],
        "net_api": "cliconf",
        "net_config": "Building configuration...\n\nCurrent configuration : 6062 bytes\n!\n! Last configuration change at 15:55:19 UTC Thu Jul 6 2023\n!\nversion 17.6\nservice timestamps debug datetime msec\nse
...output omitted...

The playbook displays facts in JSON format as a dictionary of variables. You can browse the output to see what facts are gathered, and to find facts that you might want to use in your plays.

The following table shows some facts that might be gathered from a managed node and which might be useful in a playbook:

You can also register the output of the *_facts resource modules to a variable. Because facts are stored in the registered variable, you need to reference the facts using the registered variable's namespace, as in the following example:

---
- name: Gather and display facts for IOS managed nodes
  hosts: ios
  gather_facts: true
  tasks:
   - name: Gather IOS facts
     cisco.ios.ios_facts:
       gather_subset:
         - all
     register: iosfacts

   - name: Display a fact
     ansible.builtin.debug:
       var: iosfacts['ansible_facts']['ansible_net_hostname']

When a fact is used in a playbook, Ansible dynamically substitutes the variable name for the fact with the corresponding value:

---
- name: Display specific facts for managed nodes
  hosts: ios
  gather_facts: false
  tasks:
    - name: Gather IOS facts
      cisco.ios.ios_facts:
        gather_subset:
          - all

    - name: Display hostname and IPv4 addresses
      ansible.builtin.debug:
        msg: >-
          The IPv4 addresses of interfaces on
          {{ ansible_facts['net_hostname'] }} are
          {{ ansible_facts['net_all_ipv4_addresses'] }}

The following output shows how Ansible was able to query the managed node and dynamically use the information to update the variable:

[user@host ~]$ ansible-navigator run factssubset.yml -m stdout

PLAY [Display specific facts for managed nodes] *******************************

TASK [Gather IOS facts] *******************************************************
ok: [iosxe2.lab.example.com]
ok: [iosxe1.lab.example.com]

TASK [Display hostname and IPv4 addresses] ************************************
ok: [iosxe2.lab.example.com] => {
    "msg": "The IPv4 addresses of interfaces on  iosxe2.lab.example.com are  ['172.25.250.21']"
}
ok: [iosxe1.lab.example.com] => {
    "msg": "The IPv4 addresses of interfaces on  iosxe1.lab.example.com are  ['172.25.250.20']"
}

PLAY RECAP ********************************************************************
iosxe1.lab.example.com     : ok=2    changed=0    unreachable=0    failed=0 ...
iosxe2.lab.example.com     : ok=2    changed=0    unreachable=0    failed=0 ...

Gather facts from different network platforms by using the appropriate facts module for each platform.

For example, the following playbook uses a different module in each task to gather facts based on the value of the network_os fact:

---
- name: Gather facts from different network platforms
  hosts: all
  gather_facts: false
  tasks:
    - name: Gather IOS facts
      cisco.ios.ios_facts:
        gather_subset:
          - all
      when: ansible_network_os == 'cisco.ios.ios'

    - name: Gather Junos facts
      junipernetworks.junos.junos_facts:
        gather_subset:
          - all
      when: ansible_network_os == 'junipernetworks.junos.junos'