We need a script to:
1/ Mass import data from production network devices into Netbox
See the table in T205897 for what needs to be imported.
2/ Keep that data in sync (authoritative source=network devices) until Netbox becomes the authoritative source (jnt or similar configures the devices based on Netbox)
I started working on it with:
https://gerrit.wikimedia.org/r/c/operations/software/netbox-deploy/+/507217
(see README for more details).