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KB44607 - NTP Functionality Changes in 9.1R8+

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Last Modified Date11/14/2020 6:19 PM

NTP Functionality Changes in 9.1R8+

 Prior to 9.1R89.1R8 and up
Polling IntervalConfigurableNot configurable
Set at standard [min poll(64sec) and max poll(1024sec)].
Number of Configurable NTP Servers2  NTP servers configurable (Primary NTP server and a Secondary NTP server)Up to 4 NTP servers are configurable
PCS SyncThe PCS sync'd time with the primary NTP server based on the configured intervalThe PCS uses ntpd daemon to sync and maintain the system date and time of day using its own logic by poling the NTP pool at the standard designated intervals.


Problem or Goal
Prior to the NTP functionality changes, the PCS used to sync time with the Primary NTP server. If the Primary NTP server was not reachable, then it would sync with the Secondary NTP server. 

The PCS would sync an incorrect time if the Primary NTP server drifted. 

Known Issues:

  • NTP fails to sync due to Default VLAN is enabled on the Internal Port. (PRS-396134)

Best Practices

  1. A minimum of three (3) NTP servers are configured after upgrading to 9.1R8 and above.
    • It is not recommended to use only one or two NTP servers.
    • Using three or more NTP servers will help protect against one incorrect time source.
    • For more information about NTP upstream quality, refer to section 5.3.3 in the NTP documentation.
Note: Four (4) NTP are recommended for best results.
  1. DNS resolution is done via internal port regardless of whether NTP is configured for the external port:
    • To change the DNS behavior, this will need to be done under Network > Overview > Port for DNS Traffic
Note: The impact of this change will send not just NTP traffic but all DNS traffic out the external port as well. 
  1. If running a Virtual Appliance, ensure that "sync host time" is disabled.
Related Links
Attachment 1 
Created ByDmitriy Melk-Karamov



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