Rebooting Network Devices with Ansible

December 20, 2019 by Sean Cavanaugh

blog_Rebooting-Network-Devices-with-Ansible

With the Red Hat Ansible Automation Platform release in November, we released over 50 network resource modules to help make automating network devices easier and more turn-key for network engineers.  In addition to the new resource modules, Andrius also discussed fact gathering enhancements in his blog post, which means with every new resource module, users gain increased fact coverage for network devices.  For this blog post I want to cover another cool enhancement that may have gone unnoticed. This is the ability for network devices to make use of the wait_for_connection module.  If you are a network engineer that has operational Ansible Playbooks that need to reboot devices or take them offline, this module will help you make more programmatic playbooks to handle disconnects.  By leveraging wait_for_connection network automation playbooks can look and behave more like playbooks for Linux or Windows hosts.

 

Table of Contents

Comparing wait_for and wait_for_connection

Dealing with prompts

Using reset_connection in combination

Where to go next?

 

Comparing wait_for and wait_for_connection 

There are two great modules that can wait for a condition to be met, wait_for and the wait_for_connection.  I highly recommend against using the pause module if you can get away with it, and I equate it to using a programming equivalent of a sleep within an Ansible Playbook.  Using either of these two wait_for modules is superior to random pauses within your Ansible Playbook because they are a more programmatic solution that is more adaptable to devices taking different amounts of time to complete a task.  The other problem with the pause module is that using prompts does not work within Ansible Tower. A much better solution for human interaction would be to use an Ansible Tower workflow with an approval node.

The wait_for module can wait until a path on a filesystem exists, or until a port is active again.  This works great for most reboot use cases, except for when a system is not able to be logged into immediately after the port is up.  The wait_for_connection extends the functionality of the wait_for use case a bit further. The wait_for_connection module will make sure that Ansible can log back into the device and receive the appropriate prompts before finishing completing the task. For Linux and Windows hosts it will use the ping or win_ping module, for network devices it will make sure the connection plugin that was last used can fully connect to the device.  At the time of this blog post this only works with the network_cli connection plugin.  This means that subsequent tasks can begin operating as intended as soon as wait_for_connection completes versus where wait_for just knows that port is open.

 

Dealing with prompts

With networking devices when we perform operational tasks such as a reboot, there is often a prompt to confirm that you want to take an action.

For example on a Juniper vSRX device:

admin@rtr3> request system reboot
Reboot the system ? [yes,no] (no)

The user has to confirm the reload to be able to proceed.  Something I neglected to cover on my deep dive with cli_command blog was that cli_command module can handle prompts. The cli_command module can even handle multiple prompts!  For this example the Cisco router had not saved its config, and we are performing a reload.  First the Cisco router will alert me that the System configuration has been modified, and ask me if I want to save this before I lose my running-configuration:

rtr1#reload

System configuration has been modified. Save? [yes/no]:

After confirming yes or no, you will receive a second prompt:

Proceed with reload? [confirm]

We need to build a task that can handle both prompts using the cli_command module:

---
- name: reboot ios device
  cli_command:
    command: reload
    prompt:
      - Save?
      - confirm
    answer:
     - y
     - y

The above task will answer yes to both prompts, saving the config and reloading the device.  The list for prompt answer and the list for answer must match and be in the same order. This means that the answer for prompt[0] must be answer[0].

If you want to see a more detailed example of handling multiple prompts, here is an example of a password reset on a Juniper vSRX device.

 

Using reset_connection in combination 

Now that you understand how to reboot the device with cli_command we can combine that with the wait_for_connection to create a reusable Ansible Playbook.  However, we need to add one more task, a meta: reset_connection to make this work programmatically.  

We need to make sure the current connection to the network device is closed so that the socket can be reestablished to the network device after the reboot takes place.  If the connection is not closed and the command timeout is longer than the time it takes to reboot, the persistent connection will attempt to reuse the closed SSH connection resulting in the failure “Socket is closed”. A correct Ansible Playbook looks like this:

- reboot task (this is a snippet, full task removed for brevity)

- name: reset the connection
  meta: reset_connection

- name: Wait for the network device to reload
  wait_for_connection:
    delay: 10

Now we have an Ansible Playbook that can reconnect to network devices after a reboot is issued!  For a full example please refer to this reboot.yml Ansible Playbook for Arista vEOS network devices.

 

Where to go next?

This blog helped outline how to create reusable Ansible Playbooks for rebooting network devices.  One of the next steps is obviously building out an Ansible Role that can reboot multiple network platforms.  I have gone ahead and created one and uploaded it to Github here.  This role will work on Juniper Junos, Cisco IOS and Arista EOS devices and can be easily modified to handle many more network operating systems.  In addition to reading the blog check out some other great content:

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Sean Cavanaugh

Sean is a Principal Product Marketing Manager, Ansible, where he brings over 10 years of experience building and automating computer networks. Sean previously worked for both Cumulus Networks and Cisco Systems where he helped customers deploy, manage and automate their network infrastructure. He resides in Chapel Hill, NC with his wife and children and tweets from @IPvSean.


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