Chapter 7 Tactical Playbooks

“Good tactics can save even the worst strategy. Bad tactics will destroy even the best strategy.” - George S. Patton.

Tactical changes are often one-time in nature and have a variable footprint. Sometimes there is a need to deploy a new feature that has configuration elements on every device on the network, such as a QoS policy or Netflow collection. Other changes might be limited to multiple touch points on one or two devices. Ansible playbooks are flexible enough to handle changes of any size or scope. Start accumulating various one-time playbooks that can be cloned as reusable templates of known working code. Quickly write new playbooks based on working code in the repository. A full history of the changes these playbooks make is now available in the change control history.

Moving Towards Automated Changes The network automation engine is being given a level of authorization to change network configurations based on the playbooks being written. Be sure that collectively everyone is ready before proceeding.

Orchestration Before starting to write any YAML think of the primary goals such as what the organization is trying to achieve with tactical playbooks. What are the requirements for the change? Which devices are impacted? Is there a specific order of operation in which to execute the commands? Is there any output that should be gathered before, during, or after the change to validate the state of the network? How can success be measured?

Ansible executes playbooks in serial fashion providing granular control and the ability to orchestrate changes across the enterprise network. Think of the steps involved in provisioning a simple VLAN on the network.

 Distribution Layer:

o New VLAN. o STP root for new VLAN. o New SVI for VLAN. o Add VLAN to port-channel facing access switch.

 Access Layer:

o New VLAN. o Add VLAN to port-channel facing distribution layer. o Configure physical interfaces as access ports on new VLAN.

Ansible translates this intent into a fully orchestrated modular playbook that can be refactored in the future for all new Access Layer VLANs.