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There are periodic leap second events which can add or delete a second to global time. When the leap second update occurs the following could be observed; 1. Nexus 1000 active VSM resets. Standby VSM switches over and becomes active. The previous active now comes up as Standby. All the VEM`s will be in same state and will not have any traffic disruption. 2. If the standby VSM is not present, the single active VSM will reset and comes up as active and the VEM`s will flap. During this time there will not be any traffic disruption. 3. No core files for the failed VSM.
The leap second update will be propagated via Network Time Protocol (NTP) or via manually setting the clock. The Nexus 1000 VSM may hit a Kernel livelock under the following 2 conditions: 1. When the NTP server pushes the update to the N1K NTPd client, which in turn schedules the update to the Kernel. This push should have happened 24 hours before June 30th 2015, by most NTP servers. 2. When the NTP server actually updates the clock 1 minute before the UTC time.
On 29th June 2015, NTP server can be disabled on VSM using the command: no ntp server On July 1st 2015, ntp can be reconfigured as earlier.
In a single VSM environment it is advised to save the running configuration using "copy r s" command on June 30, If the mentioned workaround is not followed.
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