How Network Automation is Different

Network automation leverages the basic Ansible concepts, but there are important differences in how the network modules work. This introduction prepares you to understand the exercises in this guide.

• Execution on the control node
• Multiple communication protocols
• Collections organized by network platform

• Privilege Escalation: enable mode, become, and authorize

  • Using become for privilege escalation

Execution on the control node

Unlike most Ansible modules, network modules do not run on the managed nodes. From a user’s point of view, network modules work like any other modules. They work with ad hoc commands, playbooks, and roles. Behind the scenes, however, network modules use a different methodology than the other (Linux/Unix and Windows) modules use. Ansible is written and executed in Python. Because the majority of network devices can not run Python, the Ansible network modules are executed on the Ansible control node, where ansible or ansible-playbook runs.

Network modules also use the control node as a destination for backup files, for those modules that offer a backup option. With Linux/Unix modules, where a configuration file already exists on the managed node(s), the backup file gets written by default in the same directory as the new, changed file. Network modules do not update configuration files on the managed nodes, because network configuration is not written in files. Network modules write backup files on the control node, usually in the backup directory under the playbook root directory.

Multiple communication protocols

Because network modules execute on the control node instead of on the managed nodes, they can support multiple communication protocols. The communication protocol (XML over SSH, CLI over SSH, API over HTTPS) selected for each network module depends on the platform and the purpose of the module. Some network modules support only one protocol; some offer a choice. The most common protocol is CLI over SSH. You set the communication protocol with the ansible_connection variable:

Value of ansible_connection	Protocol	Requires	Persistent?
ansible.netcommon.network_cli	CLI over SSH	network_os setting	yes
ansible.netcommon.netconf	XML over SSH	network_os setting	yes
ansible.netcommon.httpapi	API over HTTP/HTTPS	network_os setting	yes
local	depends on provider	provider setting	no

The ansible_connection: local has been deprecated. Please use one of the persistent connection types listed above instead. With persistent connections, you can define the hosts and credentials only once, rather than in every task. You also need to set the network_os variable for the specific network platform you are communicating with. For more details on using each connection type on various platforms, see the platform-specific pages.

Collections organized by network platform

A network platform is a set of network devices with a common operating system that can be managed by an Ansible collection, for example:

• Arista: arista.eos
• Cisco: cisco.ios, cisco.iosxr, cisco.nxos
• Juniper: junipernetworks.junos
• VyOS vyos.vyos

All modules within a network platform share certain requirements. Some network platforms have specific differences - see the platform-specific documentation for details.

Privilege Escalation: enable mode, become, and authorize

Several network platforms support privilege escalation, where certain tasks must be done by a privileged user. On network devices this is called the enable mode (the equivalent of sudo in *nix administration). Ansible network modules offer privilege escalation for those network devices that support it. For details of which platforms support enable mode, with examples of how to use it, see the platform-specific documentation.

Using become for privilege escalation

Use the top-level Ansible parameter become: yes with become_method: enable to run a task, play, or playbook with escalated privileges on any network platform that supports privilege escalation. You must use either connection: network_cli or connection: httpapi with become: yes with become_method: enable. If you are using network_cli to connect Ansible to your network devices, a group_vars file would look like:

ansible_connection: ansible.netcommon.network_cli
ansible_network_os: cisco.ios.ios
ansible_become: yes
ansible_become_method: enable

For more information, see Become and Networks