Just wondering about the "actual" NTP clock Stratum version requirements when
installing Cisco CUCM. As the three sources below show varying results;
So first we have the install guides;
Cisco recommends that you use an external NTP server to ensure accurate system time on the first node. Ensure the external NTP server is stratum 9 or higher (meaning stratums 1-9). Subsequent nodes in the cluster will get their time from the first node.When you are installing Cisco Unity Connection on a virtual machine, you must specify an external NTP server.
Then the SRND;
Unified CM automatically synchronizes the NTP time of all subscribers in the cluster to the publisher. During installation, each subscriber is automatically configured to point to an NTP server running on the publisher. The publisher considers itself to be a master server and provides time for the cluster based on its internal hardware clock unless it is configured to synchronize from an external server. Cisco highly recommends configuring the publisher to point to a Stratum-1, Stratum-2, or Stratum-3 NTP server to ensure that the cluster time is synchronized with an external time source.
And finally the NTP White Paper;
For Cisco Unified CallManager Versions 5.0 and later:
– Cisco Unified CallManager prompts the administrator to specify the external NTP server at publisher installation and automatically populates the ntpd.conf file on the publisher server.
– The ntpd.conf files of all other cluster servers are automatically configured to point to the publisher as the NTP source.
• Configure the publisher to point to a traceable stratum 1 clock source.
• Configure network latency between the publisher and the dedicated clock source so that it is within 40 milliseconds round-trip time (RTT).
Thanks for any light you can shed on this.
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we also experienced this discrepancy on this deployment, anyway we just followed the SRND - besides having a more reliable clocking will lead to stability and help us a lot on our troubleshooting.
Actually, my question in reference to the OS administration guide on NTP settings (Versions 5.x up to 10.X has this note)
"NOTE: After deleting, modifying, or adding NTP server, you must restart all the other nodes in the cluster for the changes to take affect."
- is a cluster reboot really required?
- what will be the impact if this is not followed?
thanks for the advice!
Answering this old post, Stratum 3 is required to be able to syncronize with a NTP Server. At the end, the Publisher will become a Stratum 4 for subscribers.
Startum 5 or higher will be rejected: "NTP servers with stratum 5 or worse clocks are deemed unreliable."
Do you have reference for this.
Still murky waters:
In 9.1 release Stratum 5 no longer enforced.
The procedure "Set up first node" has been updated to remove the requirement that the external NTP server be Stratum 5 or higher. When you configure the first node, Cisco recommends configuring the publisher to point to a Stratum 1, Stratum 2, or Stratum 3 NTP server to ensure that the cluster time is synchronized with an external time source.
No, but you can use my own personal experiences as a reference :). I have test this on a production system.
At least for CUCM9.1, NTP Stratum 5 or higher will not work, maybe will work just for the initial installation process.
I have a customer running cucm 18.104.22.16800-9 with Stratum 5. They are getting NTP alert every minute. Does this mean Stratum isn't recommended for this cucm version?
admin:utils diagnose module ntp_stratum
Log file: platform/log/diag2.log
Starting diagnostic test(s)
test - ntp_stratum : Failed
The reference NTP server is a stratum 5 clock.
NTP servers with stratum 5 or worse clocks are deemed unreliable.
Please consider using an NTP server with better stratum level.
Please use OS Admin GUI to add/delete NTP servers.
(For people who come to this thread from Google search)
Doc from TAC has been published recently to address NTP troubleshooting.