Documentation

Network Best Practices for Ansible 2.5

Overview

This document explains the best practices for using Ansible 2.5 to manage your network infrastructure.

Audience

  • This example is intended for network or system administrators who want to understand how to use Ansible to manage network devices.

Prerequisites

This example requires the following:

  • Ansible 2.5 (or higher) installed. See Installation Guide 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.

Concepts

This section explains some fundamental concepts that you should understand when working with Ansible Networking.

Structure

The examples on this page use the following structure:

.
├── facts-demo.yml
└── inventory

Inventory, Connections, Credentials: Grouping Devices and Variables

An inventory file is an 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. Here’s what it would look like if you specified your ssh passwords (encrypted with Ansible Vault) among your variables:

[all:vars]
# these defaults can be overridden for any group in the [group:vars] section
ansible_connection=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=eos
ansible_user=my_eos_user
ansible_ssh_pass= !vault |
                  $ANSIBLE_VAULT;1.1;AES256
                  37373735393636643261383066383235363664386633386432343236663533343730353361653735
                  6131363539383931353931653533356337353539373165320a316465383138636532343463633236
                  37623064393838353962386262643230303438323065356133373930646331623731656163623333
                  3431353332343530650a373038366364316135383063356531633066343434623631303166626532
                  9562

[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=ios
ansible_user=my_ios_user
ansible_ssh_pass= !vault |
                  $ANSIBLE_VAULT;1.1;AES256
                  34623431313336343132373235313066376238386138316466636437653938623965383732373130
                  3466363834613161386538393463663861636437653866620a373136356366623765373530633735
                  34323262363835346637346261653137626539343534643962376139366330626135393365353739
                  3431373064656165320a333834613461613338626161633733343566666630366133623265303563
                  8472

[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
ansible_user=my_vyos_user
ansible_ssh_pass= !vault |
                  $ANSIBLE_VAULT;1.1;AES256
                  39336231636137663964343966653162353431333566633762393034646462353062633264303765
                  6331643066663534383564343537343334633031656538370a333737656236393835383863306466
                  62633364653238323333633337313163616566383836643030336631333431623631396364663533
                  3665626431626532630a353564323566316162613432373738333064366130303637616239396438
                  9853

If you use ssh-agent, you do not need the ansible_ssh_pass 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 the Connecting to hosts: behavioral inventory parameters.

Warning

Never store passwords in plain text.

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 Vault in playbooks for more information.

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 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 network_cli or netconf.
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_ssh_pass:
 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 eos and 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 version 2.5 added support for become when using connection: 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=network_cli
ansible_network_os=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 doesn’t 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.

Playbook

Collect data

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 eos_facts, ios_facts and vyos_facts to connect to the remote networking device. As the credentials are not explicitly passed via 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 eos_facts and 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 The When Statement.

Example

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.

Create an inventory file

First, create a file called inventory, containing:

[switches:children]
eos
ios
vyos

[eos]
eos01.example.net

[ios]
ios01.example.net

[vyos]
vyos01.example.net

Create a 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)
      eos_facts:
      when: ansible_network_os == 'eos'

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

    - name: Gather facts (vyos)
      vyos_facts:
      when: ansible_network_os == '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)
      eos_config:
        backup: yes
      register: backup_eos_location
      when: ansible_network_os == 'eos'

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

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

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.

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 Accessing information about other hosts with magic variables.

Get running configuration

The eos_config and 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.