A registration token is generated from Mist UI to onboard devices like SSR and SRX.

For routers that are managed by Conductors and added to Mist for telemetry, the registration code can be added to Conductor which then pushes it out to the managed routers.

The validity of registration token is 1 year from the date it was generated. There would be warnings/alerts generated on the router when the token is expired.