With YANG there is NO need to model device completely and then migrate – it is completely normal to model only part of the functionality and automate it. Recommended way is:
- Choose a service to automate
- Cover what is possible with vendor-neutral YANG models, identify their gaps
- Choose workarounds to fill the gaps. Creation of proprietary YANG models is the priority, CLI/SNMP is less desirable
- Define a plan to replace the workarounds with vendor-neutral YANG models
- Deploy
It is suggested to have centrally governed, but collectively populated repository of vendor-neutral YANG models. It will simplify navigation in a huge number of YANG models available from various sources, streamline adoption, versioning and knowledge sharing.