Our earth is very slowly slowing down, which means every now and then scientists call to add an extra second to our time to compensate. The last was in 2012, the next one is coming up on June 30, 2015 23:59:60 UTC. For more information about this leap second, check timeanddate.com.
Cisco posted an impact analysis on their website with links to bug reports which determine the impact. While most campus products are unaffected, there are some warnings on datacenter products where the leap second update can lead to a crash or lockup.
My intention is not to scare, but to have this post serve as a notice to check whether something in your environment may be affected. Cisco uses a lot of ‘may crash’ and ‘may lockup’ in the bug reports, so my understanding is that it is not a guarantee that it will happen, just that there is a chance. But I’d rather not take that chance. 😉
Below is a summary of the datacenter products, but for the full product list check the Cisco website.
| Product | Impact | Workaround | Cisco Bug |
| Nexus 1000v | Possible active VSM reset | Disable NTP config | CSCus80369 |
|
MDS 9000 Series MDS 9513 MDS 9509 MDS 9506 MDS 9222i MDS 9148 MDS 8-Gb Fabric Switch for HP c-Class Blade System MDS 9134 MDS 9124 MDS 4-Gbps Fabric Switch for HP c-Class BladeSystem MDS 4-Gbps Fabric Switch for IBM BladeCenter |
Switch doesn’t understand leap second | Non-disruptively resync time | CSCut22182 |
| Nexus 3000 Series | If PTP is enabled, a skew of max 35 seconds can be observed | Disable PTP, increase TTL or upgrade to a known fix. | CSCui37256 |
| Nexus 5010/5500 Series | Switches running NX-OS 5.0, 5.1 5.2 may lock up. | Disable NTP config or upgrade to a known fix. | CSCub38654 |
| Nexus 5010/5500 Series | If PTP is enabled, a skew of max 35 seconds can be observed | Disable PTP, increase TTL or upgrade to a known fix. | CSCut81357 |
| Nexus 6000 Series | Switches running NX-OS 5.0, 5.1 5.2 may lock up. | Disable NTP config or upgrade to a known fix. | CSCub38654 |
| Nexus 7000 (SUP 1 only) | Affected NX-OS versions may experience a livelock. | Disable NTP config or upgrade to a known fix. | CSCua77416 |
| Nexus 9000 Series | If PTP is enabled, a skew of max 35 seconds can be observed | Disable PTP, increase TTL or upgrade to a known fix. | CSCut78541 |
| Unified Computing System (UCS) Manager Unified Computing System (UCS) Fabric Interconnect Unified Computing System (UCS) C-Series Rack Mount UCS-Managed Server SW |
System could crash causing a network outage. Versions 2.0 & 2.1 are unaffected. | Disable NTP config or upgrade to a known fix. | CSCus83447 |
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