NTP issue with Cisco Meraki Network

Last updated on December 31, 2020

Background 

Neat devices require NTP (Network Time Protocol) server for a variety of functions, and a valid NTP server is a requirement when setting up and operating these devices.

When a Neat device is first connected to the network, it uses DHCP (Dynamic Host Configuration Protocol) to obtain its IP address and various other network details (gateway, DNS server etc.). DHCP can also provide additional options, such as the NTP server using the ‘DHCP option 42’.

‘DHCP option 42′ support on Neat

Until early March 2020, Neat devices did not support DHCP option 42 as a method for NTP configuration. Instead, Neat came preconfigured with its own NTP server details (time.neat.no) and any DHCP option 42 parameters (provided by the DHCP server) were ignored.

From March 2020, Neat devices introduced the ability to change the default NTP server (time.neat.no) to a different one either manually, or using DHCP option 42.

Issue specific to Cisco Meraki networks 

Cisco Meraki networks have a known behaviour wherein, if no valid NTP server is configured by the network administrator, the Meraki Gateway populates the ‘DHCP option 42’ field with its own IP address. However, Meraki Gateway is not an NTP server and therefore it doesn’t respond to any NTP traffic. 

If a Neat device is configured in such a setup, it will pick up the DHCP option 42 as its NTP server (in this case, the Meraki Gateway) and start sending NTP requests to this IP address. However, since Meraki does not respond to these requests, Neat device thinks the NTP server is unavailable and in turn presumes its own status as offline (it will display the message ’Not connected to the internet’ or similar). 

For new installations or units that have been factory-reset (e.g. after an upgrade to the latest version that supports DHCP option 42), the user will not be able to advance forward through the initial setup screens.

For installed units (those that pre-dates the DHCP option 42 support), once they are upgraded to the latest software version, various time-dependent operations will be affected that may potentially make the system unusable (e.g. wrong calendar displays, inability to connect to the Zoom cloud etc.).   

Solution 

  • Configure a valid DHCP option 42 for the network (so that Meraki gateway does not try to populate this field with its own IP address).
  • OR, disable DHCP option 42 in the Meraki configuration (Neat will continue to use time.neat.no NTP server as its default).