.. _network-best-practices:

************************
Ansible Network Examples
************************

This document describes some examples of using Ansible to manage your network infrastructure.

.. contents::
   :local:

Prerequisites
=============

This example requires the following:

* **Ansible 2.10** (or higher) installed. See :ref:`intro_installation_guide` for more information.
* One or more network devices that are compatible with Ansible.
* Basic understanding of YAML :ref:`yaml_syntax`.
* Basic understanding of Jinja2 templates. See :ref:`playbooks_templating` for more information.
* Basic Linux command line use.
* Basic knowledge of network switch & router configurations.


Groups and variables in an inventory file
=========================================

An ``inventory`` file is a YAML or INI-like configuration file that defines the mapping of hosts into groups.

In our example, the inventory file defines the groups ``eos``, ``ios``, ``vyos`` and a "group of groups" called ``switches``. Further details about subgroups and inventory files can be found in the :ref:`Ansible inventory Group documentation <subgroups>`.

Because Ansible is a flexible tool, there are a number of ways to specify connection information and credentials. We recommend using the ``[my_group:vars]`` capability in your inventory file.

.. code-block:: ini

   [all:vars]
   # these defaults can be overridden for any group in the [group:vars] section
   ansible_connection=ansible.netcommon.network_cli
   ansible_user=ansible

   [switches:children]
   eos
   ios
   vyos

   [eos]
   veos01 ansible_host=veos-01.example.net
   veos02 ansible_host=veos-02.example.net
   veos03 ansible_host=veos-03.example.net
   veos04 ansible_host=veos-04.example.net

   [eos:vars]
   ansible_become=yes
   ansible_become_method=enable
   ansible_network_os=arista.eos.eos
   ansible_user=my_eos_user
   ansible_password=my_eos_password

   [ios]
   ios01 ansible_host=ios-01.example.net
   ios02 ansible_host=ios-02.example.net
   ios03 ansible_host=ios-03.example.net

   [ios:vars]
   ansible_become=yes
   ansible_become_method=enable
   ansible_network_os=cisco.ios.ios
   ansible_user=my_ios_user
   ansible_password=my_ios_password

   [vyos]
   vyos01 ansible_host=vyos-01.example.net
   vyos02 ansible_host=vyos-02.example.net
   vyos03 ansible_host=vyos-03.example.net

   [vyos:vars]
   ansible_network_os=vyos.vyos.vyos
   ansible_user=my_vyos_user
   ansible_password=my_vyos_password

If you use ssh-agent, you do not need the ``ansible_password`` lines. If you use ssh keys, but not ssh-agent, and you have multiple keys, specify the key to use for each connection in the ``[group:vars]`` section with ``ansible_ssh_private_key_file=/path/to/correct/key``. For more information on ``ansible_ssh_`` options see :ref:`behavioral_parameters`.

.. FIXME FUTURE Gundalow - Link to network auth & proxy page (to be written)

.. warning:: Never store passwords in plain text.

Ansible vault for password encryption
-------------------------------------

The "Vault" feature of Ansible allows you to keep sensitive data such as passwords or keys in encrypted files, rather than as plain text in your playbooks or roles. These vault files can then be distributed or placed in source control. See :ref:`playbooks_vault` for more information.

Here's what it would look like if you specified your SSH passwords (encrypted with Ansible Vault) among your variables:

.. code-block:: yaml

   ansible_connection: ansible.netcommon.network_cli
   ansible_network_os: vyos.vyos.vyos
   ansible_user: my_vyos_user
   ansible_ssh_pass: !vault |
                     $ANSIBLE_VAULT;1.1;AES256
                     39336231636137663964343966653162353431333566633762393034646462353062633264303765
                     6331643066663534383564343537343334633031656538370a333737656236393835383863306466
                     62633364653238323333633337313163616566383836643030336631333431623631396364663533
                     3665626431626532630a353564323566316162613432373738333064366130303637616239396438
                     9853

Common inventory variables
--------------------------

The following variables are common for all platforms in the inventory, though they can be overwritten for a particular inventory group or host.

:ansible_connection:

  Ansible uses the ansible-connection setting to determine how to connect to a remote device. When working with Ansible Networking, set this to an appropriate network connection option, such as ``ansible.netcommon.network_cli``, so Ansible treats the remote node as a network device with a limited Execution Environment. Without this setting, Ansible would attempt to use ssh to connect to the remote and execute the Python script on the network device, which would fail because Python generally isn't available on network devices.
:ansible_network_os:
  Informs Ansible which Network platform this hosts corresponds to. This is required when using the ``ansible.netcommon.*`` connection options.
:ansible_user: The user to connect to the remote device (switch) as. Without this the user that is running ``ansible-playbook`` would be used.
  Specifies which user on the network device the connection
:ansible_password:
  The corresponding password for ``ansible_user`` to log in as. If not specified SSH key will be used.
:ansible_become:
  If enable mode (privilege mode) should be used, see the next section.
:ansible_become_method:
  Which type of `become` should be used, for ``network_cli`` the only valid choice is ``enable``.

Privilege escalation
--------------------

Certain network platforms, such as Arista EOS and Cisco IOS, have the concept of different privilege modes. Certain network modules, such as those that modify system state including users, will only work in high privilege states. Ansible supports ``become`` when using ``connection: ansible.netcommon.network_cli``. This allows privileges to be raised for the specific tasks that need them. Adding ``become: yes`` and ``become_method: enable`` informs Ansible to go into privilege mode before executing the task, as shown here:

.. code-block:: ini

   [eos:vars]
   ansible_connection=ansible.netcommon.network_cli
   ansible_network_os=arista.eos.eos
   ansible_become=yes
   ansible_become_method=enable

For more information, see the :ref:`using become with network modules<become_network>` guide.


Jump hosts
----------

If the Ansible control node does not have a direct route to the remote device and you need to use a Jump Host, please see the :ref:`Ansible Network Proxy Command <network_delegate_to_vs_ProxyCommand>` guide for details on how to achieve this.

Example 1: collecting facts and creating backup files with a playbook
=====================================================================

Ansible facts modules gather system information 'facts' that are available to the rest of your playbook.

Ansible Networking ships with a number of network-specific facts modules. In this example, we use the ``_facts`` modules :ansplugin:`arista.eos.eos_facts <arista.eos.eos_facts#module>`, :ansplugin:`cisco.ios.ios_facts <cisco.ios.ios_facts#module>` and :ansplugin:`vyos.vyos.vyos_facts <vyos.vyos.vyos_facts#module>` to connect to the remote networking device. As the credentials are not explicitly passed with module arguments, Ansible uses the username and password from the inventory file.

Ansible's "Network Fact modules" gather information from the system and store the results in facts prefixed with ``ansible_net_``. The data collected by these modules is documented in the `Return Values` section of the module docs, in this case :ansplugin:`arista.eos.eos_facts <arista.eos.eos_facts#module>` and :ansplugin:`vyos.vyos.vyos_facts <vyos.vyos.vyos_facts#module>`. We can use the facts, such as ``ansible_net_version`` late on in the "Display some facts" task.

To ensure we call the correct mode (``*_facts``) the task is conditionally run based on the group defined in the inventory file, for more information on the use of conditionals in Ansible Playbooks see :ref:`the_when_statement`.

In this example, we will create an inventory file containing some network switches, then run a playbook to connect to the network devices and return some information about them.

Step 1: Creating the inventory
------------------------------

First, create a file called ``inventory``, containing:

.. code-block:: ini

   [switches:children]
   eos
   ios
   vyos

   [eos]
   eos01.example.net

   [ios]
   ios01.example.net

   [vyos]
   vyos01.example.net


Step 2: Creating the playbook
-----------------------------

Next, create a playbook file called ``facts-demo.yml`` containing the following:

.. code-block:: yaml

   - name: "Demonstrate connecting to switches"
     hosts: switches
     gather_facts: no

     tasks:
       ###
       # Collect data
       #
       - name: Gather facts (eos)
         arista.eos.eos_facts:
         when: ansible_network_os == 'arista.eos.eos'

       - name: Gather facts (ios)
         cisco.ios.ios_facts:
         when: ansible_network_os == 'cisco.ios.ios'

       - name: Gather facts (vyos)
         vyos.vyos.vyos_facts:
         when: ansible_network_os == 'vyos.vyos.vyos'

       ###
       # Demonstrate variables
       #
       - name: Display some facts
         debug:
           msg: "The hostname is {{ ansible_net_hostname }} and the OS is {{ ansible_net_version }}"

       - name: Facts from a specific host
         debug:
           var: hostvars['vyos01.example.net']

       - name: Write facts to disk using a template
         copy:
           content: |
             #jinja2: lstrip_blocks: True
             EOS device info:
               {% for host in groups['eos'] %}
               Hostname: {{ hostvars[host].ansible_net_hostname }}
               Version: {{ hostvars[host].ansible_net_version }}
               Model: {{ hostvars[host].ansible_net_model }}
               Serial: {{ hostvars[host].ansible_net_serialnum }}
               {% endfor %}

             IOS device info:
               {% for host in groups['ios'] %}
               Hostname: {{ hostvars[host].ansible_net_hostname }}
               Version: {{ hostvars[host].ansible_net_version }}
               Model: {{ hostvars[host].ansible_net_model }}
               Serial: {{ hostvars[host].ansible_net_serialnum }}
               {% endfor %}

             VyOS device info:
               {% for host in groups['vyos'] %}
               Hostname: {{ hostvars[host].ansible_net_hostname }}
               Version: {{ hostvars[host].ansible_net_version }}
               Model: {{ hostvars[host].ansible_net_model }}
               Serial: {{ hostvars[host].ansible_net_serialnum }}
               {% endfor %}
           dest: /tmp/switch-facts
         run_once: yes

       ###
       # Get running configuration
       #

       - name: Backup switch (eos)
         arista.eos.eos_config:
           backup: yes
         register: backup_eos_location
         when: ansible_network_os == 'arista.eos.eos'

       - name: backup switch (vyos)
         vyos.vyos.vyos_config:
           backup: yes
         register: backup_vyos_location
         when: ansible_network_os == 'vyos.vyos.vyos'

       - name: Create backup dir
         file:
           path: "/tmp/backups/{{ inventory_hostname }}"
           state: directory
           recurse: yes

       - name: Copy backup files into /tmp/backups/ (eos)
         copy:
           src: "{{ backup_eos_location.backup_path }}"
           dest: "/tmp/backups/{{ inventory_hostname }}/{{ inventory_hostname }}.bck"
         when: ansible_network_os == 'arista.eos.eos'

       - name: Copy backup files into /tmp/backups/ (vyos)
         copy:
           src: "{{ backup_vyos_location.backup_path }}"
           dest: "/tmp/backups/{{ inventory_hostname }}/{{ inventory_hostname }}.bck"
         when: ansible_network_os == 'vyos.vyos.vyos'

Step 3: Running the playbook
----------------------------

To run the playbook, run the following from a console prompt:

.. code-block:: console

   ansible-playbook -i inventory facts-demo.yml

This should return output similar to the following:

.. code-block:: console

   PLAY RECAP
   eos01.example.net          : ok=7    changed=2    unreachable=0    failed=0
   ios01.example.net          : ok=7    changed=2    unreachable=0    failed=0
   vyos01.example.net         : ok=6    changed=2    unreachable=0    failed=0

Step 4: Examining the playbook results
--------------------------------------

Next, look at the contents of the file we created containing the switch facts:

.. code-block:: console

   cat /tmp/switch-facts

You can also look at the backup files:

.. code-block:: console

   find /tmp/backups


If `ansible-playbook` fails, please follow the debug steps in :ref:`network_debug_troubleshooting`.


.. _network-independent-examples:

Example 2: simplifying playbooks with platform-independent modules
==================================================================

(This example originally appeared in the `Deep Dive on cli_command for Network Automation <https://www.ansible.com/blog/deep-dive-on-cli-command-for-network-automation>`_ blog post by Sean Cavanaugh -`@IPvSean <https://github.com/IPvSean>`_).

If you have two or more network platforms in your environment, you can use the platform-independent modules to simplify your playbooks. You can use platform-independent modules such as ``ansible.netcommon.cli_command`` or ``ansible.netcommon.cli_config`` in place of the platform-specific modules such as ``arista.eos.eos_config``, ``cisco.ios.ios_config``, and ``junipernetworks.junos.junos_config``. This reduces the number of tasks and conditionals you need in your playbooks.

.. note::
  Platform-independent modules require the :ansplugin:`ansible.netcommon.network_cli <ansible.netcommon.network_cli#connection>` connection plugin.


Sample playbook with platform-specific modules
----------------------------------------------

This example assumes three platforms, Arista EOS, Cisco NXOS, and Juniper JunOS.  Without the platform-independent modules, a sample playbook might contain the following three tasks with platform-specific commands:

.. code-block:: yaml

  ---
  - name: Run Arista command
    arista.eos.eos_command:
      commands: show ip int br
    when: ansible_network_os == 'arista.eos.eos'

  - name: Run Cisco NXOS command
    cisco.nxos.nxos_command:
      commands: show ip int br
    when: ansible_network_os == 'cisco.nxos.nxos'

  - name: Run Vyos command
    vyos.vyos.vyos_command:
      commands: show interface
    when: ansible_network_os == 'vyos.vyos.vyos'

Simplified playbook with ``cli_command`` platform-independent module
--------------------------------------------------------------------

You can replace these platform-specific modules with the platform-independent ``ansible.netcommon.cli_command`` module as follows:

.. code-block:: yaml

  ---
  - hosts: network
    gather_facts: false
    connection: ansible.netcommon.network_cli

    tasks:
      - name: Run cli_command on Arista and display results
        block:
        - name: Run cli_command on Arista
          ansible.netcommon.cli_command:
            command: show ip int br
          register: result

        - name: Display result to terminal window
          debug:
            var: result.stdout_lines
        when: ansible_network_os == 'arista.eos.eos'

      - name: Run cli_command on Cisco IOS and display results
        block:
        - name: Run cli_command on Cisco IOS
          ansible.netcommon.cli_command:
            command: show ip int br
          register: result

        - name: Display result to terminal window
          debug:
            var: result.stdout_lines
        when: ansible_network_os == 'cisco.ios.ios'

      - name: Run cli_command on Vyos and display results
        block:
        - name: Run cli_command on Vyos
          ansible.netcommon.cli_command:
            command: show interfaces
          register: result

        - name: Display result to terminal window
          debug:
            var: result.stdout_lines
        when: ansible_network_os == 'vyos.vyos.vyos'


If you use groups and group_vars by platform type, this playbook can be further simplified to :

.. code-block:: yaml

  ---
  - name: Run command and print to terminal window
    hosts: routers
    gather_facts: false

    tasks:
      - name: Run show command
        ansible.netcommon.cli_command:
          command: "{{show_interfaces}}"
        register: command_output


You can see a full example of this using group_vars and also a configuration backup example at `Platform-independent examples <https://github.com/network-automation/agnostic_example>`_.

Using multiple prompts with the  ``ansible.netcommon.cli_command``
-------------------------------------------------------------------

The ``ansible.netcommon.cli_command`` also supports multiple prompts.

.. code-block:: yaml

  ---
  - name: Change password to default
    ansible.netcommon.cli_command:
      command: "{{ item }}"
      prompt:
        - "New password"
        - "Retype new password"
      answer:
        - "mypassword123"
        - "mypassword123"
      check_all: True
    loop:
      - "configure"
      - "rollback"
      - "set system root-authentication plain-text-password"
      - "commit"

See the :ref:`ansible.netcommon.cli_command <cli_command_module>` for full documentation on this command.


Implementation Notes
====================


Demo variables
--------------

Although these tasks are not needed to write data to disk, they are used in this example to demonstrate some methods of accessing facts about the given devices or a named host.

Ansible ``hostvars`` allows you to access variables from a named host. Without this we would return the details for the current host, rather than the named host.

For more information, see :ref:`magic_variables_and_hostvars`.

Get running configuration
-------------------------

The :ansplugin:`arista.eos.eos_config <arista.eos.eos_config#module>` and :ansplugin:`vyos.vyos.vyos_config <vyos.vyos.vyos_config#module>` modules have a ``backup:`` option that when set will cause the module to create a full backup of the current ``running-config`` from the remote device before any changes are made. The backup file is written to the ``backup`` folder in the playbook root directory. If the directory does not exist, it is created.

To demonstrate how we can move the backup file to a different location, we register the result and move the file to the path stored in ``backup_path``.

Note that when using variables from tasks in this way we use double quotes (``"``) and double curly-brackets (``{{...}}`` to tell Ansible that this is a variable.

Troubleshooting
===============

If you receive an connection error please double check the inventory and playbook for typos or missing lines. If the issue still occurs follow the debug steps in :ref:`network_debug_troubleshooting`.

.. seealso::

  * :ref:`network_guide`
  * :ref:`intro_inventory`
  * :ref:`Keeping vaulted variables visible <tip_for_variables_and_vaults>`
