We have briefly talked about the addition of network connection changes in Ansible playbooks, starting with version 2.5. Along with the changes, Ansible also released a network best practices document, https://docs.ansible.com/ansible/latest/network/user_guide/network_best_practices_2.5.html. Let's build an example based on the best practices guide. For our topology, we will reuse the topology in Chapter 5, Low-Level Network Device Interactions, with two IOSv devices. Since there are multiple files involved in this example, the files are grouped into a subdirectory named ansible_2-5_example. 

Our inventory file is reduced to the group and the name of the hosts: 

$ cat hosts
[ios-devices]
iosv-1
iosv-2

We have created a host_vars directory with two files. Each corresponds to the name specified in the inventory file: 

$ ls -a host_vars/
. .. iosv-1 iosv-2

The variable file for the hosts contains what was previously included in the CLI variable. The additional variable of ansible_connection specifies network_cli as the transport:

$ cat host_vars/iosv-1
---
ansible_host: 172.16.1.20
ansible_user: cisco
ansible_ssh_pass: cisco
ansible_connection: network_cli
ansible_network_os: ios
ansbile_become: yes
ansible_become_method: enable
ansible_become_pass: cisco

$ cat host_vars/iosv-2
---
ansible_host: 172.16.1.21
ansible_user: cisco
ansible_ssh_pass: cisco
ansible_connection: network_cli
ansible_network_os: ios
ansbile_become: yes
ansible_become_method: enable
ansible_become_pass: cisco

Our playbook will use the ios_config module with the backup option enabled. Notice the use of the when condition in this example so that if there are other hosts with a different operating system, this task will not be applied:

$ cat my_playbook.yml
---
- name: Chapter 4 Ansible 2.5 Best Practice Demonstration
  connection: network_cli
  gather_facts: false
  hosts: all
  tasks:
    - name: backup
      ios_config:
        backup: yes
      register: backup_ios_location
      when: ansible_network_os == 'ios'

When the playbook is run, a new backup folder will be created with the configuration backed up for each of the hosts: 

$ ansible-playbook -i hosts my_playbook.yml

PLAY [Chapter 4 Ansible 2.5 Best Practice Demonstration] ***********************

TASK [backup] ******************************************************************
ok: [iosv-2]
ok: [iosv-1]

PLAY RECAP *********************************************************************
iosv-1 : ok=1 changed=0 unreachable=0 failed=0
iosv-2 : ok=1 changed=0 unreachable=0 failed=0

$ ls -l backup/
total 8
-rw-rw-r-- 1 echou echou 3996 Jul 11 19:01 iosv-1_config.2018-07-11@19:01:55
-rw-rw-r-- 1 echou echou 3996 Jul 11 19:01 iosv-2_config.2018-07-11@19:01:55

$ cat backup/iosv-1_config.2018-07-11@19:01:55
Building configuration...


Current configuration : 3927 bytes
!
! Last configuration change at 01:46:00 UTC Thu Jul 12 2018 by cisco
!
version 15.6
service timestamps debug datetime msec
service timestamps log datetime msec
...

This example illustrates the network_connection variable and the recommended structure based on network best practices. We will look at offloading variables into the host_vars directory and conditionals in Chapter 8, The Python Automation Framework – Beyond Basics. This structure can also be used for the Juniper and Arista examples in this chapter. For the different devices, we will just use different values for network_connection.