Domain 1 of 4 · Chapter 5 of 6

Selecting the Network Automation Approach

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Included in this chapter:

  • One rule, four questions
  • How much to build: low-code, IaC, custom
  • Expressing intent: declarative vs imperative
  • Talking to the device: model-driven vs CLI
  • Which Cisco platform: match the scope
  • NSO: one transaction across vendors
  • Reading the stem: which approach does the scenario want?

Choosing an automation approach by decision factor

Decision factorIaC frameworkLow-code/no-codeCustom application
Coding skill neededModerate (YAML or HCL)Low to noneHigh (Python and APIs)
FlexibilityHigh within the framework's modelLow, limited to prebuilt blocksHighest, any logic
Speed to valueMedium, after learning the toolFastestSlowest, you build it first
Scale across a fleetStrong, one definition to many devicesStrong within the controller's scopeDepends on what you build
Maintainability / ownershipTeam owns playbooks and modulesVendor owns the blocksTeam owns the whole app
Typical Cisco toolingAnsible, TerraformCatalyst Center templates and workflowsPython app on device and platform APIs

Decision tree

Fits a prebuilt block?YesLow-code / no-codeCatalyst CenterNoBespoke multi-system logic?YesCustom applicationPython on APIsNoMany devices, repeatable?YesIaC frameworkAnsible, TerraformNoShort script or templateone-off changeRule: buy the least capability that meets the requirement
Cheat sheet

Cheat sheet

  • IaC frameworks give declarative, versionable, idempotent config
  • Low-code/no-code trades flexibility for speed and low skill
  • Custom applications maximize flexibility at higher cost
  • Approach selection weighs scale, skills, flexibility, maintainability
  • Declarative tools converge on a desired end state
  • Imperative approaches require you to manage steps and idempotency
  • Idempotency is a core selection criterion
  • Model-driven interfaces beat CLI scraping for robustness
  • NSO uses a transactional CDB and FASTMAP for service orchestration
  • Catalyst Center Intent API and SD-WAN vManage API automate fabrics
  • Match the platform to the automation scope

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References

  1. https://docs.python.org/3/
  2. https://developer.cisco.com/docs/dna-center/
  3. https://docs.ansible.com/ansible/latest/network/getting_started/network_differences.html
  4. https://developer.hashicorp.com/terraform/intro
  5. https://developer.hashicorp.com/terraform/cli/commands/plan
  6. https://developer.hashicorp.com/terraform/language/state
  7. https://docs.ansible.com/ansible/latest/network/user_guide/network_resource_modules.html
  8. https://www.rfc-editor.org/rfc/rfc8040
  9. https://datatracker.ietf.org/doc/html/rfc7231
  10. https://docs.ansible.com/ansible/latest/reference_appendices/glossary.html
  11. https://docs.ansible.com/ansible/latest/collections/cisco/ios/ios_config_module.html
  12. https://datatracker.ietf.org/doc/html/rfc7950
  13. https://datatracker.ietf.org/doc/html/rfc6241
  14. https://developer.cisco.com/iosxe/
  15. https://ncclient.readthedocs.io/en/latest/manager.html
  16. https://developer.cisco.com/docs/nso/guides/managing-network-services/
  17. https://developer.cisco.com/docs/nso/guides/network-element-drivers-and-adding-devices/