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Exercise 6.2 - An introduction to templating with Jinja2

Jinja2 is a powerful templating engine for Python. There is native integration of Jinja2 with Ansible. Jinja2 allows for manipulating variables and implementing logical constructs. In combination with the Ansible template module, the automation engineer has a powerful tool at their disposal to generate live or dynamic reports.

In this lab you will learn how to use the template module to pass collected data from devices to a Jinja2 template.

Step 1

This time, we'll use a Jinja2 template to create the payload for the cli_config task. First, take a look at the Jinja2 template ios-ntp-cli.j2:

$ cat templates/ios-ntp-cli.j2
{% for server in ntp_servers %}
ntp server {{ server }}
{% endfor %}

Notice that it simply iterates over the elements in the ntp_servers list and outputs ntp server {{ server }} for each server.

Now create a new playbook called cli-template.yml and add the following play definition that uses this template into it:

- name: CONFIGURE ROUTERS
  hosts: routers
  gather_facts: no
  connection: network_cli
  vars:
    ntp_servers:
        - 192.5.41.40
        - 192.5.41.41

  tasks:
    - name: ENSURE THAT THE DESIRED NTP SERVERS ARE PRESENT
      cli_config:
        config: "{{ lookup('template', 'ios-ntp-cli.j2') }}"

Note: We are now using the cli_config module that is network OS (vendor) agnostic. It uses the variable ansible_network_os that we've set in the inventory to determine how to talk to the target device.

Finaly, run the playbook:

$ ansible-playbook cli-template.yml

PLAY [CONFIGURE ROUTERS] ***********************************************************************************************************************

TASK [ENSURE THAT THE DESIRED NTP SERVERS ARE PRESENT] *****************************************************************************************
ok: [sp1]
ok: [hq]
ok: [core]
ok: [internet]

PLAY RECAP *************************************************************************************************************************************
core                       : ok=1    changed=0    unreachable=0    failed=0
hq                         : ok=1    changed=0    unreachable=0    failed=0
internet                   : ok=1    changed=0    unreachable=0    failed=0
sp1                        : ok=1    changed=0    unreachable=0    failed=0

Note: That Ansible automatically looks in the templates directory for templates.

Note: Run with -vvv to see the output from the template being fed into the cli_config module.

Step 2

Now create a new playbook called netconf-template.yml and add the following play definition to it:

- name: CONFIGURE ROUTERS
  hosts: routers
  gather_facts: no
  connection: netconf
  vars:
    ntp_servers:
        - 192.5.41.40
        - 192.5.41.41
        
  tasks:
    - name: ENABLE NETCONF/YANG ON THE ROUTER
      cli_config:
        config: netconf-yang
      connection: network_cli
        
    - name: ENSURE THAT THE DESIRED NTP SERVERS ARE PRESENT
      netconf_rpc:
        rpc: edit-config
        content: "{{ lookup('template', 'ios-ntp-netconf.j2') }}"

Note: We first need to enable NETCONF on the target device using connection type network_cli.

Now run the playbook:

$ ansible-playbook netconf-template.yml

PLAY [CONFIGURE ROUTERS] ***********************************************************************************************************************

TASK [ENABLE NETCONF/YANG ON THE ROUTER] *******************************************************************************************************
ok: [internet]
ok: [core]
ok: [hq]
ok: [sp1]

TASK [ENSURE THAT THE DESIRED NTP SERVERS ARE PRESENT] *****************************************************************************************
ok: [core]
ok: [sp1]
ok: [hq]
ok: [internet]

PLAY RECAP *************************************************************************************************************************************
core                       : ok=2    changed=0    unreachable=0    failed=0
hq                         : ok=2    changed=0    unreachable=0    failed=0
internet                   : ok=2    changed=0    unreachable=0    failed=0
sp1                        : ok=2    changed=0    unreachable=0    failed=0

Complete

You have completed lab exercise 6.2

Click Here to return to the Viptela Networking Automation Workshop