Leap Second

Ready for Leap-Second Adjustment?

Information for our customers and partners on the global introduction of the leap second adjustment planned for December 31, 2016.

Ready for Leap-Second Adjustment?

To ensure correct alignment of astronomical and atomic time, the International Earth Rotation and Reference Systems Service requested that an extra second be added to Coordinated Universal Time (UTC) at 23:59:59 on December 31, 2016.

The 27th leap-second adjustment since 1972 represents an important consideration for providers of computing, networking, and software solutions.

Cisco Response

In July 2016, the International Earth Rotation and Reference Systems Service announced the planned introduction of a leap second. As a result, Cisco assembled a team to assess potential impacts for our products, services, and customers. The team prepared a comprehensive list of affected Cisco platforms and is working with our engineering teams to validate the reaction (if any) to the introduced leap second. This site provides the results of the team's due diligence and includes ongoing updates for our customers.

Cisco Experience 2008, 2012, and 2015

As part of Cisco’s preparation for the 2016 leap second, we completed a comprehensive review of past customer support cases. This included a detailed search of service requests, defects, and bug reports, focusing on the period 1 week either side of the 2008, 2012, and 2015 leap-second introductions.

We assessed the related records for all three periods, spanning all Cisco platforms and all Cisco customers, and found a limited number of defects and service requests. Although one of these customers required a system reboot to recover, most experienced synchronization alarms, which were easily and quickly resolved with support from the Cisco Technical Assistance Center (TAC). As a result, we do not believe that the previous leap-second adjustments represented any material events for our products or customers.

Updated: August 4, 2016

Q: What is a leap second?
Due to occasional irregularities in the Earth's rotation, it is possible for a difference in astronomical and atomic times to occur. When that difference exceeds 0.9 of a second, the International Earth Rotation & Reference Systems Service calls for a leap second to be added or subtracted to Coordinated Universal Time (UTC).

Q: Why is this important?
Time is an important component of modern computing, with many equipment, software, and application providers relying on Coordinated Universal Time (UTC) for their solutions to function effectively. Consequently, the introduction of the leap second is an important consideration for all technology providers and their customers.

Q: When will the leap second be introduced?
At the direction of the International Earth Rotation and Reference Systems Service (see bulletin), the leap second will be introduced after 23:59:59, December 31, 2016. The clock then will read 23:59:60 before it rolls over to 00:00:00, January 1, 2017. This is a one-time event that occurs simultaneously across the globe.

Q: Is this the first leap second introduction?
No. The 2016 leap-second adjustment is the 27th since 1972.

Q: What happened last time?
Despite online commentary predicting widespread technology failures, there were no widely reported related impacts as the result of the 2012 and 2015 leap-second introductions. There were some incidents of online systems and customer applications not managing the extra second gracefully.

Q: What was the previous experience for Cisco customers?
We do not believe that the last three leap-second adjustments (2008, 2012, and 2015) represented any material events for our products or customers. We completed a detailed search of all service requests, defects, and bug reports, focusing on the period 1 week either side of the recent leap-second introductions. A limited number of defects and service requests were found. Although one customer required a system reboot to recover, these reports related mostly to synchronization alarms that were quickly and easily resolved with support from the Cisco Technical Assistance Center (TAC).

Q: What has Cisco done in response?
After the International Earth Rotation and Reference Systems Service issued its bulletin, Cisco assembled a team to assess potential impacts for our products, services, and customers. The team prepared a comprehensive list of Cisco platforms and has been working with our engineering teams to validate the reactions (if any) to an introduced leap second.

Q: How will Cisco solutions respond to the 2016 leap second?
We will provide details of how Cisco products are expected to respond to the 2016 leap second on the Product Information tab. This includes classification of products with no expected impacts and possible impacts (updates not yet provided).

Q: Is this a security concern?
We do not consider the leap-second introduction a product security vulnerability. Where a possible impact is identified, it is classified as a product bug and managed accordingly. All qualified customers with current service contracts are eligible for software updates.

Q: How do you recommend customers prepare for the leap second?
We recommend visiting the Product Information tab to understand what impact, if any, there may be for Cisco products in your network. We also recommend reviewing leap-second advice from other technology and software providers in your organization.

Q: Will Cisco provide software and other updates to manage the leap second?
Yes. Where a possible impact has been identified, Cisco plans to provide software updates to all qualified customers with current service contracts.

Q: When will these updates be available?
Many updates will be available by early October 2016 and can be found on the Product Information tab. This site also provide details of new updates as they become available.

Q: Will updates be provided for end-of-life or end-of-support products?
No. Many platforms do not require a software update, but updates are provided only to qualified customers and for completely supported Cisco platforms. This is consistent with the Cisco's End-of-Life Policy.

Q: How do you define the No Expected Impact product category?
All products listed in this section have been subjected to reviews by the appropriate engineering team. These teams did not observe any material impacts of a simulated leap second being introduced for the listed products. End-of-life and end-of-support products were not reviewed.

Q: Is there any impact to a network supporting Precision Time Protocol (PTP)?
The majority of Cisco products do not implement PTP, and there should be no impact to these products. However, there are several Cisco routing and switching products that support PTP and can be affected by a PTP leap-second event if running as a PTP boundary clock. For more information, see the Product Information tab for products and release notes marked with PTP.

Q: What advice do you have for devices that have PTP configured for time synchronization?
If your device is configured to use PTP as a boundary clock, then an incorrect Coordinated Universal Time (UTC) offset and PTP leap indicator can propagate incorrect time downstream. The UTC and PTP leap-second-indication events are received properly from the PTP grandmaster clock; however, the Cisco device acting as the PTP boundary clock can move forward incorrectly and thus corrupt the downstream version of time.

Updated: 24 December 2016

Following a comprehensive review by the Cisco leap second team, we are pleased to offer the following information. Our experience of the 2008, 2012 and 2015 leap second introductions, combined with our recent assessment of potential impacts for our current solutions, suggest that the leap second introduction is unlikely to represent a material event for Cisco products in our customers’ networks.

Collaboration and Social Media

Product Family Release Note
Show and Share CSCut08830
Telepresence Conductor CSCut30576
No Expected Impact
Cisco® Meeting Place

Cisco Telepresence Content Server

Meeting App Windows / OS X / iOS

All WebEx® products
Cisco Jabber®

Cisco TelePresence®

Meeting Server X Series / VMware / Hyper-V

Network Application, Service, and Acceleration

Product Family Release Note
Cisco GSS Global Site Selector CSCut33302
No Expected Impact
Cisco Intercloud Fabric

Cisco CloudCenter

Cisco Nexus® Fabric Manager

Network and Content Security Devices

Product Family Release Note
Cisco NAC Appliance (Clean Access) CSCva94173, CSCva94190
Cisco NAC Guest Server CSCva94173, CSCva94190
Cisco Identity Services Engine CSCva94541
Secure Access Control Server CSCva81649
Cisco ASA 5500-X Series Firewalls CSCuv11738
No Expected Impact
Cisco Adaptive Security Appliance

Cisco Adaptive Security Virtual Appliance

Cisco Adaptive Security Device Manager

ASA Device Package

Cisco Security Manager

Cisco FirePOWER™ Series Appliances

Cisco FireSIGHT® Management Center

Cisco IPS Series Sensors

Cisco AnyConnect Secure Mobility Clie

nt Cisco Web Security Appliance

Cisco Cloud Email Security
Cisco Email Security Appliance

Cisco Email Encryption Appliance

Cisco Content Security Management Appliance

Cisco Secure Access Control Server Solution Engine

Cisco Secure Access Control Server for Windows

Cisco Secure Access Control System

Cisco Umbrella

Cisco Cloud Web Security



Cisco Registered Envelope Service

Network Management and Provisioning

Product Family Release Note
Cisco Nexus 1000v (KVM, Vmware, HyperV, VSG) CSCus80369
Cisco Nexus 1100 (CSP) CSCus80369
Cisco Prime™ IP Express CSCut08887
Cisco Prime Network Registrar CSCus99802, CSCut08713
Cisco Prime Central CSCvb03061
No Expected Impact
Cisco Access Registrar


Cisco Elastic Services Controller

Cisco Intelligent Automation for Cloud

Cisco InterCloud Fabric

Cisco Multicast Manager

Cisco Netflow Generation Agent (NGA)

Cisco Netflow Generation 3000 Series Appliance

Cisco Network Services Orchestrator (NSO)

Cisco OpenStack

Cisco Performance Agent

Cisco Prime Active Catalog

Cisco Prime Cable Provisioning

Cisco Prime Fulfillment

Cisco Prime Fulfillment (Multi-Vendor Service Orchestration)

Cisco Prime Network Services Controller
Cisco Prime LAN Management Solution (LMS)

Cisco Prime Network

Cisco Prime Network Analysis Module, vNAM

Cisco Prime Optical

Cisco Prime Order Fulfillment

Cisco Prime Performance Manager

Cisco Prime Provisioning

Cisco Prime Service Catalog

Cisco Process Orchestrator

Cisco Virtual Application Container Services

Cisco Virtual Managed Services Solution

Cisco Virtual Topology System

Cisco WAN Automation Engine (WAE)

Cisco Works Compliance Manager

Cisco Prime Infrastructure


Routing and Switching - Enterprise and Service Provider

Product Family Release Note
Network Convergence System 6000 Series CSCut08955
Cisco MDS 9000 Series Multilayer Switches CSCut22182
Cisco Nexus 3000 Series Switches CSCui37256

Cisco Nexus 5000 Series Switches CSCub38654,

CSCut81357 (PTP)
Cisco Nexus 6000 Series Switches CSCub38654
Cisco Nexus 7000 Series Switches CSCuv11862

Cisco Nexus 9000 Series Switches CSCut78541 CSCvb03418
Cisco 7600 series CSCua73674, CSCty99593
Cisco 7200 CSCua73674
Cisco ME 1200 series CSCvb27525
Cisco ME 3600X/3800X series CSCua73674, CSCvb09408
Cisco VG Series Gateways CSCua73674
Cisco ASR 900/920 series CSCvb09497

CSCul73513, CSCua73674

CSCvb01920, CSCvb01730
Cisco ASR 901 CSCvb04040
Cisco ISR 4400/4300 series CSCvb19326

CSCul73513, CSCua73674,

CSR1000v series CSCvb19326

CSCul73513 CSCua73674,

ASR 1000 CSCvb19326





CSCut65374 (PTP)
Cisco Application Networking Manager (ANM) OVA CSCut50034
Cisco Nexus 4000 Series CSCut50569
Catalyst 6000 Series CSCua73674
Cisco Industrial Ethernet 3000 Series Switch CSCua73674
Cisco Industrial Ethernet 4000, 5000 Series Switches CSCvb04298
Cisco Mobility Services Engine CSCva66512
Cisco Connected Mobile Experiences CSCva66498
ASR 9000 Series CSCva37964
No Expected Impact
Application Centric Infrastructure (ACI)

Application Policy Infrastructure Controller (APIC)

Catalyst 2000, 3000, 4000 series


Cisco Application Networking Manager (ANM)


Cisco ACE 10 & 20 Application Control Engine


Cisco ACE 30 Application Control Engine Module

Cisco ACE 4700 Series Application Control Engine


Cisco Industrial Router (IR) 900 Series

Cisco Network Analysis Module

Cisco Nexus Series 2000

Cisco ONS 15000 and ONS 15000E series

Cisco Wide Area Application Services (WAAS)

Content Services Switch

Cisco 500, 800 Series WPAN Industrial Router

Cisco 1000, 2000 Series Connected Grid Router

Cisco Network Convergence System 1000, 2000, 4000, 5000, 5500 Series


NCS 2000, 4000 series


UBR 10000

UBR 7200

Cisco 800/800M

Cisco 1900/2900/3900/3900E

WAAS Central Manager

Cisco AppNav

Cisco Aironet 600, 700,1500,

1600,2600,3600,1700,2700,3700 Series

Cisco Aironet 3800, 2800, 1800, 1500 Series

Cisco Wireless Controller 2500, 5500, 5700,

8500 series

Cisco Small Business 100, 300, 500, 600

Series Wireless Access Points

Cisco Industrial Wireless 3700 series

Cisco 5900 Series Embedded Services Router

Cisco Edge 300 Series

Cisco 3000 Series Industrial Security Appliances

Cisco Industrial Ethernet 1000, 2000

Series Switches

Unified Computing

Product Family Release Note
Cisco UCS® Manager

Cisco UCS C-Series Rack Mount Cisco UCS Managed Server SW
Cisco Unified Computing System (Cisco UCS) Invicta Appliance

Cisco Unified Computing System (Cisco UCS) Invicta Scaling System

Cisco Unified Computing System (Cisco UCS) Invicta Legacy 4.x
Cisco Unified Computing System (Cisco UCS) Fabric Interconnect CSCus83447
No Expected Impact
Integrated Management Controller (IMC) Supervisor

Cisco Unified Computing System (Cisco UCS)

Central SW

Cisco Unified Computing System (Cisco UCS)

Director SW

Cisco Unified Computing System (Cisco UCS)

Standalone C-Series Products

Cisco UCS-M 3.0 Releases

Cisco UCS Mini

Unified Computing System (Cisco UCS)

Management Partner Ecosystem SW

Unified Computing System (Cisco UCS)

Performance Manager

Unified Computing System (Cisco UCS)

Standalone C-Series SW

Cisco HyperFlex Systems

Voice and Unified Communication Devices

Product Family Release Note
Cisco Emergency Responder CSCut09811
Unity Connection CSCut25526
Cisco Hosted Collaboration Mediation Fulfilment CSCut05305
Cisco Unified Communications Manager (CUCM) CSCut25356
Cisco Unified SIP Proxy (CUSP) CSCut07923
Enhanced Survivable Remote Site (E-SRST) Manager CSCut07923
MXE 3500 series CSCut08092
Cisco Unity® Express CSCut07923
Cisco Unified Border Element CSCtz61014
Communications Manager Express (CME) and Cisco Unified

Survivable Remote Site Telephony (SRST)
Cisco Unified Communications Manager IM and Presence Server CSCut62475
Unified Contact Center Express/IP IVR CSCut16832
Cisco Unified Intelligence Center CSCut57780
Mediasense CSCut12363
Cisco Finesse® CSCut59282
Cisco Prime Collaboration Assurance CSCva99488
Cisco Prime Collaboration Analytics CSCva99488
Expressway-Core CSCva69072
Expressway-Edge (incl both appliance and virtual machine base deployment) CSCva69072
Video Communication Server (VCS)-Control CSCva69072
Video Communication Server (VCS)-Expressway CSCva69072
No Expected Impact
Advance Media AM gateway 3610

Contact Center Domain Manager

Cisco Contact Center Management Portal

Cisco Email Interaction Manager/Web Interaction


Cisco IP Communicator 8.6

Cisco TelePresence ISDN Link

Cisco Unified Attendant Console

Cisco Unified Communications Domain Manager

version 10

Conference Director

Contact Center Management Portal

CVP Customer Voice Portal

Hosted Collaboration Solution for Contact Center

IP gateway 8350, 3510, 3520, 3540

IP Phone - 69xx, 78xx, 79xx, 88xx, 89xx, 99xx

IP VCR 8220, 2210, 2215 and 2240

Call Service Aware

Call Service Connect

Calendar Service

Cisco Vision Dynamic Signage Director

Cisco Agent Desktop for UCCE

Video Communication Server (VCS) Expressway

Starter Pack

Cisco Prime License Manager
TelePresence ISDN GW MSE 8321, 8341

and 3241

Media Processing Systems MPS 200/800

Cisco Telepresence Supervisor MSE 8050

Cisco Telepresence MCU 4200, 4500, 5300

series, MSE 8510 and MSE 8420


Packaged Contact Center Enterprise

Cisco Prime Collaboration Provisioning

Cisco Telepresence Serial gateway 8330 and 3340

Singlewire / Cisco Paging Server


TelePresence Server MSE 8710, 7010, virtual

TelePresence Server, Media 310 and 320

DX Systems

IX Systems



Unified Contact Center Enterprise

Cisco Voice Browser

Voice GatewayVG2xx, VG2xxXM


Cisco Work Force Optimization

Cisco Remote Silent Monitor

TelePresence™ Software - EX, SX, C-Series and MX

Cisco Unified Communications Domain Manager

Video, Streaming, TelePresence, and Transcoding Devices

Product Family Release Note
Cisco Digital Media Player 4310G and 4400G CSCuu76403
No Expected Impact
Cisco CDS Internet Streaming

Cisco TelePresence Manager

CTMS TelePresence Multipoint Switch

CTRS Cisco TelePresence Recording Server

CTX TelePresence Exchange System

Desktop DX/ES Series (Endpoints)

TelePresence Management Suite

TelePresence Management System TMS-AE

Cisco TelePresence Extension for MS


TelePresence Management System TMS-PE

TelePresence Management System TMS-XE

TelePresence Management System TMS-XN

Mobility and Wireless

Product Family Release Note
ASR5000/StarOS CSCut09843
ASR5500/StarOS CSCus80022
QVPC-SI/StarOS CSCus98712
QVPC-DI/StarOS CSCut06846
Embedded Service Switch L-ESS CSCvb26879, CSCvb26882
No Expected Impact

Cisco Policy Suite

Mobility Unified Reporting and Analytics MURAL

Cisco Gateway GPRS Support Node (GGSN) on

Service and Application Module for IP (SAMI)

Cisco Content Services Gateway-Second Generation

(CSG2) on SAMI

Cisco Long Term Evolution (LTE) Serving

Gateway/PDN Gateway (SPGW) on SAMI

Policy and Charing Enforcement Function (PCEF) on


Cisco Wireless Security Gateway (WSG) on SAMI

Wireless LAN Controllers

  • Integrated Controllers and Controller Modules
  • Cisco Wireless Controller Software for SRE
  • Cisco Wireless Services Module 2 (WiSM2)
Mobility Unified Reporting MUR

Web Element Manager WEM

Standalone Controllers

  • Cisco 8500 Series Wireless Controllers
  • Cisco 5700 Series Wireless LAN Controllers
  • Cisco 5500 Series Wireless Controllers
  • Cisco 2500 Series Wireless Controllers
  • Cisco Flex® 7500 Series Wireless Controllers
  • Cisco Virtual Wireless Controller

SP Video

Product Family Release Note
Integrated Receiver Decoder (IRD) CSCut10139
Cisco Modular Encoding Platform D9036 CSCut10139
Cisco PowerVu CSCut10139
Videoscape VDS TV CSCut06887
Digital Content Manager (DCM) CSCut14146
ROSA Network and Video Service Management CSCut14146
Cisco Visual Quality Experience (VQE) CSCvb11089
No Expected Impact

Class A CHS 335HDC

Class B CHS 435HDC

Client Fusion Cable

Client Fusion Satellite

Common Download Server CDLS

Conditional Access CA/Digital Rights Management DRM

Conductor, DLS, TED


Digital Network Control System DNCS


Enterprise Content Delivery System (ECDS)


Evolution Middleware

Explorer Series running PowerTV OS (Explorer 1800

through Explorer 8742)

Explorer 46xx, Explorer 86xx, Explorer 98xx, Explorer 58xx

Fusion Cable

Fusion Satellite

Open Media

Video Media Recorder (VMR)

IPTV Service Delivery System ISDS

Mean Option Score MOS

Remote Conditional Access Server RCAS


RNG Series Running PowerTV OS

(RNG100, RNG150, RNG200...)


Video Back Office VBO

Videoscape AnyRes

Videoscape Session Resource Manager,VSRM/RM

Videoscape VDS-IS


Infinite Home

Infinite Video

Infinite Broadcast


Cisco Prime Home

D9800 IRD

Additional Guidance

Our review of past leap-second introductions revealed that similar platforms responded differently across multiple customer networks. This difference suggests that variations in network and application topography can be factors in customers’ experiences. For this reason, we also recommend:

  • Appropriate deployment of Network Time Protocol (NTP) sources and strata
  • Consistency of NTP versions on the network
  • Management of common time-driven alarms

As always, we recommend contacting the Cisco Technical Assistance Center (TAC) immediately if you observe rejected calls, loss of normal functionality, or high CPU levels that do not quickly return to normal levels.

Technical Questions

Please contact your Cisco account representative or Cisco Technical Assistance Center (TAC).

Media Enquires

Nigel Glennie
Global Corporate Communications