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Cisco Bug: CSCut65324 - PTP Leap Second : ASR9k PTP: Handle upcoming leapsecond on Jun 30 2015

Last Modified

Jul 30, 2018

Products (7)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9922 Router
  • Cisco IOS XR Software
  • Cisco ASR 9010 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9912 Router

Known Affected Releases


Description (partial)

There are periodic leap second events which can add or delete a second to global time. The leap second event can be propagated via Precision Time Protocol (PTP) if configured.

When the leap second update occurs and the device is configured to use PTP as a Boundary Clock (BC) then an incorrect Coordinated Universal Time (UTC) offset and PTP Leap Indicator could propagate incorrect time downstream. This could cause the PTP network time to be off as much as thirty five seconds.

The next leapsecond is announced for 2015, which will be added at 30-Jun-15 23:59:59 UTC.  Customers deploying ASR9K as PTP Grandmaster or PTP Slave might be impacted due to this. 

ASR 9K as PTP Grandmaster
If ASR9K is acting as PTP Grandmaster using GPS UTC time reference,  the leapsecond correction currently done is only for 35 seconds.  Post 30-Jun-2015,  this might impact PTP slave devices which are synchronized to the master as the correction should account for the newly added leapsecond. 

ASR9K as PTP Slave
If the PTP recovered time is used to update the system time using PTP-NTP interworking feature, the system time will be offset from UTC time by one second post 30-Jun-2015

The leap second update is propagated from the configured PTP Grandmaster clock.

A Cisco device running the PTP protocol would have the "feature ptp" command in the running configuration.

ASR9K acting as PTP Grandmaster with a GPS time reference providing time in UTC timescale or
ASR9k acting as PTP Slave with PTP-NTP interworking feature  are impacted post Jun 30, 2015.
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