When Catalyst 9300 switches are onboarded to the Meraki Dashboard in “Monitor-only” or “Device Configuration” mode, their DHCP server function remains local (IOS-XE), the Meraki Dashboard does not have visibility into DHCP lease tables from the switch.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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