Ansible Network Examples

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

Prerequisites

This example requires the following:

  • Ansible 2.10 (or higher) installed. See Installing Ansible for more information.

  • One or more network devices that are compatible with Ansible.

  • Basic understanding of YAML YAML Syntax.

  • Basic understanding of Jinja2 templates. See Templating (Jinja2) 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 Ansible inventory Group documentation.

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.

[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 Connecting to hosts: behavioral inventory parameters.

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 Using encrypted variables and files for more information.

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

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:

[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 using become with network modules guide.

Jump hosts

If the Ansible Controller does not have a direct route to the remote device and you need to use a Jump Host, please see the Ansible Network Proxy Command 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 arista.eos.eos_facts, cisco.ios.ios_facts and vyos.vyos.vyos_facts 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 arista.eos.eos_facts and vyos.vyos.vyos_facts. 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 Basic conditionals with when.

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:

[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:

- 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:

ansible-playbook -i inventory facts-demo.yml

This should return output similar to the following:

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:

cat /tmp/switch-facts

You can also look at the backup files:

find /tmp/backups

If ansible-playbook fails, please follow the debug steps in Network Debug and Troubleshooting Guide.

Example 2: simplifying playbooks with network agnostic modules

(This example originally appeared in the Deep Dive on cli_command for Network Automation blog post by Sean Cavanaugh -@IPvSean).

If you have two or more network platforms in your environment, you can use the network agnostic modules to simplify your playbooks. You can use network agnostic 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

Network agnostic modules require the ansible.netcommon.network_cli connection plugin.

Sample playbook with platform-specific modules

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

---
- 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 network agnostic module

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

---
- 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 :

---
- 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 Network agnostic examples.

Using multiple prompts with the ansible.netcommon.cli_command

The ansible.netcommon.cli_command also supports multiple prompts.

---
- 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 ansible.netcommon.cli_command 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 Information about Ansible: magic variables.

Get running configuration

The arista.eos.eos_config and vyos.vyos.vyos_config 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 Network Debug and Troubleshooting Guide.

See also