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Starting with Ansible version 2.1, you can now use the familiar Ansible models of playbook authoring and module development to manage heterogenous networking devices. Ansible supports a growing number of network devices using both CLI over SSH and API (when available) transports.
Most standard Ansible modules are designed to work with Linux/Unix or Windows machines and will not work with networking devices. Some modules (including “slurp”, “raw”, and “setup”) are platform-agnostic and will work with networking devices.
To see what modules are available for networking devices, please browse the “networking” section of the Ansible module index.
All core networking modules implement a provider argument, which is a collection of arguments used to define the characteristics of how to connect to the device. This section will assist in understanding how the provider argument is used.
Each core network module supports an underlying operating system and transport. The operating system is a one-to-one match with the module, and the transport maintains a one-to-many relationship to the operating system as appropriate. Some network operating systems only have a single transport option.
Each core network module supports some basic arguments for configuring the transport:
Individual modules can set defaults for these arguments to common values that match device default configuration settings. For instance, the default value for transport is universally ‘cli’. Some modules support other values such as EOS (eapi) and NXOS (nxapi), while some only support ‘cli’. All arguments are fully documented for each module.
By allowing individual tasks to set the transport arguments independently, modules that use different transport mechanisms and authentication credentials can be combined as necessary.
One downside to this approach is that every task needs to include the required arguments. This is where the provider argument comes into play. The provider argument accepts keyword arguments and passes them through to the task to assign connection and authentication parameters.
The following two config modules are essentially identical (using nxos_config) as an example but it applies to all core networking modules:
---
nxos_config:
src: config.j2
host: "{{ inventory_hostname }}"
username: "{{ ansible_ssh_user }}"
password: "{{ ansible_ssh_pass }}"
transport: cli
---
vars:
cli:
host: "{{ inventory_hostname }}"
username: "{{ ansible_ssh_user }}"
password: "{{ ansible_ssh_pass }} "
transport: cli
nxos_config:
src: config.j2
provider: "{{ cli }}"
Given the above two examples that are equivalent, the arguments can also be used to establish precedence and defaults. Consider the following example:
---
vars:
cli:
host: "{{ inventory_hostname }}"
username: operator
password: secret
transport: cli
tasks:
- nxos_config:
src: config.j2
provider: "{{ cli }}"
username: admin
password: admin
In this example, the values of admin for username and admin for password will override the values of operator in cli[‘username’] and secret in cli[‘password’])
This is true for all values in the provider including transport. So you could have a singular task that is now supported over CLI or NXAPI (assuming the configuration is value).
---
vars:
cli:
host: "{{ inventory_hostname }}"
username: operator
password: secret
transport: cli
tasks:
- nxos_config:
src: config.j2
provider: "{{ cli }}"
transport: nxapi
If all values are provided via the provider argument, the rules for requirements are still honored for the module. For instance, take the following scenario:
---
vars:
conn:
password: cisco_pass
transport: cli
tasks:
- nxos_config:
src: config.j2
provider: "{{ conn }}"
Running the above task will cause an error to be generated with a message that required parameters are missing.
"msg": "missing required arguments: username,host"
Overall, this provides a very granular level of control over how credentials are used with modules. It provides the playbook designer maximum control for changing context during a playbook run as needed.
The following environment variables are available to Ansible networking modules:
username ANSIBLE_NET_USERNAME password ANSIBLE_NET_PASSWORD ssh_keyfile ANSIBLE_NET_SSH_KEYFILE authorize ANSIBLE_NET_AUTHORIZE auth_pass ANSIBLE_NET_AUTH_PASS
Variables are evaulated in the following order, listed from lowest to highest priority:
Ansible allows you to use conditionals to control the flow of your playbooks. Ansible networking command modules use the following unique conditional statements.
Conditional statements evalute the results from the commands that are executed remotely on the device. Once the task executes the command set, the waitfor argument can be used to evalute the results before returning control to the Ansible playbook.
For example:
---
- name: wait for interface to be admin enabled
eos_command:
commands:
- show interface Ethernet4 | json
waitfor:
- "result[0].interfaces.Ethernet4.interfaceStatus eq connected"
In the above example task, the command show interface Ethernet4 | json
is executed on the remote device and the results are evaluated. If
the path
(result[0].interfaces.Ethernet4.interfaceStatus) is not equal to
“connected”, then the command is retried. This process continues
until either the condition is satisfied or the number of retries has
expired (by default, this is 10 retries at 1 second intervals).
The commands module can also evaluate more than one set of command results in an interface. For instance:
---
- name: wait for interfaces to be admin enabled
eos_command:
commands:
- show interface Ethernet4 | json
- show interface Ethernet5 | json
waitfor:
- "result[0].interfaces.Ethernet4.interfaceStatus eq connected"
- "result[1].interfaces.Ethernet4.interfaceStatus eq connected"
In the above example, two commands are executed on the remote device, and the results are evaluated. By specifying the result index value (0 or 1), the correct result output is checked against the conditional.
The waitfor argument must always start with result and then the command index in [], where 0 is the first command in the commands list, 1 is the second command, 2 is the third and so on.