1. 查看设备的display clock信息，结果如下与当前北京时间不同步：
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2018-05-11 02:01:32-05:13
Friday
Time Zone(Indian Standard Time) : UTC-05:13
2. display ntp-service event clock-unsync查看时钟不同步的原因为Clock selection failed - No selectable clock，详细结果如下：
<TY-XZX-CE01-S5700>disp ntp-service event clock-unsync
1. Clock source : 10.86.X.X
Session type : client, configured
Unsync reason : Clock selection failed - No selectable clock
Unsync time : 2018-05-11 01:25:26-05:13
2. Clock source : 10.86.X.X
Session type : client, configured
Unsync reason : Clock selection failed - No selectable clock
Unsync time : 2018-05-11 01:35:08-05:13
3. 查看logbuffer日志 有重复系统同步源丢失日志，截取部分如下：
May 11 2018 01:54:26-05:13 TY-XZX-CE01-S5700 %%01NTP/4/SOURCE_LOST(l)[0]:System synchronization source lost. (SourceAddress=10.86.X.X, Reason=Clock selection failed - No selectable clock)
May 11 2018 01:53:21-05:13 TY-XZX-CE01-S5700 %%01NTP/4/STRATUM_CHANGE(l)[1]:System stratum changes from 16 to 3. (SourceAddress=10.86.X.X.)
May 11 2018 01:53:21-05:13 TY-XZX-CE01-S5700 %%01NTP/4/LEAP_CHANGE(l)[2]:System leap changes from 3 to 0 after clock update.
May 11 2018 01:53:21-05:13 TY-XZX-CE01-S5700 %%01NTP/4/PEER_SELE(l)[3]:The peer selected by the system is 10.86.X.X.
May 11 2018 01:44:50-05:13 TY-XZX-CE01-S5700 %%01NTP/4/SOURCE_LOST(l)[4]:System synchronization source lost. (SourceAddress=10.86.X.X., Reason=Clock selection failed - No selectable clock)
4. 通过debugging ntp-service all结果来看应该就是同步距离过大导致设备失步：
May 11 2018 02:28:52.50.2-05:13 TY-XZX-CE01-S5700 NTP/7/NTP_DBG_Selection:
FileId [ 019 ], LineNo [ 00536 ]- Server 10.86.x.x not considered for clock selection. (Reason: Synchronization distance greater than distance threshold. (Current: 3.95522,
Allowable: 1.00048))
