[All About Switches]NTP Clock Synchronization Delays for Seconds Due to NTP Configuration Faults on Modular Switches

Created: Mar 15, 2018 11:35:03Latest reply: Jun 3, 2018 22:00:22 1482 2 0 0

Involved Products and Versions

All models and versions


An S series switch is connected to a Windows server. The S series switch functions as the NTP client, and the Windows server functions as the NTP server.

Fault Symptom

A delay occurs and lasts for seconds when the S series switch that functions as the NTP client synchronizes the clock of the NTP server.

Cause Analysis

The configurations are incorrect. The local NTP clock is configured on the S series switch, and the stratum of the local clock is higher than that of the peer NTP server. As a result, the S series switch selects the local NTP clock and does not synchronize the clock of the peer NTP server. In this case, the time of the S series switch is different from that of the NTP server.

Troubleshooting Procedure

1.         Log in to the S series switch, and run the display ntp-service status command in any view to check the NTP clock status. It is found that the device uses the local clock rather than that of the peer NTP server. Run the display current-configuration | include ntp command to view NTP configurations. The command output shows that the local clock is configured.

<HUAWEI> display ntp-service status  
clock status: synchronized 
clock stratum: 2             ----The stratum of the local clock is 2.
reference clock ID: LOCAL(0) ----The local clock instead of the clock of the peer NTP server is used.
nominal frequency: 100.0000 Hz 
actual frequency: 100.0005 Hz 
clock precision: 2^18
clock offset: 0.0000 ms 
root delay: 0.00 ms 
root dispersion: 10.93 ms 
peer dispersion: 10.00 ms 
reference time: 09:32:03.344 UTC Jun 22 2017(DCF60D13.5849FD7A)
<HUAWEI> display current-configuration | include  ntp
ntp-service refclock-master 2 ----------The local clock with stratum being 2 is configured.
ntp-service unicast-server
ntp-service unicast-server

2.         Run the display ntp-service sessions verbose command in any view to view the details of the NTP session.

<HUAWEI> display ntp sessions verbose  
clock source: 
clock stratum: 9 ------------The clock stratum is 9, and the stratum is lower than that of the local clock (the NTP layer has a negative correlation with the clock stratum), so the local clock is used.
clock status: configured, insane, invalid
reference clock ID:
local mode: client, local poll: 6
peer mode: server, peer poll: 6
offset: 35227.0247 ms,delay: 6.43 ms, disper: 189.32 ms
root delay: 0.00 ms, root disper: 962.91 ms
reach: 377, sync dist: 38.981, sync state: 4
precision: 2^6, version: 3, peer interface: wildcard
reftime: 10:48:54.562 UTC Jun 21 2017(DCF4CD96.8FE62563)
orgtime: 09:33:02.780 UTC Jun 22 2017(DCF60D4E.C7B4FE79)
rcvtime: 09:32:24.351 UTC Jun 22 2017(DCF60D28.59F4D37C)
xmttime: 09:32:24.343 UTC Jun 22 2017(DCF60D28.580B34E7)
filter delay : 0.01 0.01 0.00 0.01 0.01 0.01 0.01 0.01
filter offset: 35.23 1.62 1.63 35.22 35.22 34.78 34.79 34.80
filter disper: 0.00 16.00 16.00 0.01 0.01 0.00 0.00 0.00

3.         To synchronize the clock of the S series switch with that of the peer NTP server, you can modify the configuration of the local NTP clock and increase the stratum of the local clock functioning as the NTP master clock. For example, change the stratum of the local clock to 11, which is greater than the number of layers synchronized by the peer server.

<HUAWEI> system-view
[HUAWEI] ntp-service refclock-master 11

4.         After the preceding modification is performed, wait for a period of time. If the delay persists, run the debugging ntp-service packet command to enable the debugging of NTP packets, and check the NTP parameters. The result shows that the rdsp root dispersion provided by the upper-layer server is large (900+ ms).

<HUAWEI> debugging ntp-service packet
... ...
0.63049778 HUAWEI NTP/8/debug_NTP_packet_rcv:
 packet from to on GigabitEthernet0/0/0
 leap: 0, version: 3, mode: 3
 stratum: 3, ppoll: 1024, precision: 2**17
 rdel: 32.883, rdsp: 900.986, refid:                  ... ...

5.         If the NTP server runs the Windows operating system, perform the following steps to change the root dispersion of the NTP server. Pay attention that this operation will restart the Windows NTP service. Exercise caution when you perform this operation.

Step 1: On the Windows server, enter regedit to access the registry, and modify the value of the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\W32Time\Config\LocalClockDispersion field to 0.

Step 2: Enter w32tm /config /update in Windows to restart the NTP service. Pay attention that this operation will restart the NTP service, and evaluate risks before performing this operation.

Conclusions and Suggestions

In this example, NTP clock synchronization on the S series switch is abnormal. You need to check whether the peer NTP server or the local server is used, and obtain the interaction information between the switch and the NTP server to determine the point of exception.

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gululu     Created Mar 15, 2018 14:05:20 Helpful(0) Helpful(0)

thanks for your sharing
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Come on!
wissal  Visitor   Created Jun 3, 2018 22:00:22 Helpful(0) Helpful(0)

useful document, thanks
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