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Is Nexus 5K running 5.2(1)N1(8b) affected by the Leap Second Update? - CSCub38654

Narcis Matasaru

I have a client running version 5.2(1)N1(8b) and wanted to know if this falls under the affected releases.


Known Nexus 5K affected releases:



Known Nexus 5K fixed releases:


CSCub38654 - N5K Switch hang/lock up may occur due to Leap second update


1 Accepted Solution

Accepted Solutions

Our NX-OS versions are not on the list either but to play it safe were disabling NTP from 29th June to 1st July anyway ,if your that unsure TAC it

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16 Replies 16

Mark Malone
VIP Alumni
VIP Alumni

Hi no your clients version should not be effected by this bug

Thanks Mark. I listed the known affected and fixed releases based on the Cisco bugsearch result listed in the question but could not find my exact release. Do you have another source for my actual version 5.2(1)N1(8b) that you could reference?

Hi your client is on the safe harbour image the most recommended one in the train by Cisco , your image is from Nov 2014 the ones effected are a year before it , you will not get any more confirmation other than the bug release , out of all the releases only 2 were effected so it very unlikely there version is as the fix would generally be in newer releases , you can check the release notes caveat section for your version but i dont see any on the Cisco website for these releases


When I go to Cisco's bug search site and enter "leap second" and nexus 5596UP as a product, it doesn't have any reference to the specific version we 5.2(1)N1(8b). Here's the search results I do get:


I'm still not convinced my version is not affected. The ones higher are listed as fixed but no mention of this:

Known Fixed Releases:

Our NX-OS versions are not on the list either but to play it safe were disabling NTP from 29th June to 1st July anyway ,if your that unsure TAC it


We are doing the same, nice to see another person going this route.  Thanks for the input.



I have a customer running the same version, 5.2(1)N1(8b) so we're gonna disable NTP as well.

Since we have two Nexus-switches we're configuring in a switch-profile.

However, I'm unable to remove the ntp server when I'm in config sync.

The negate command does not exist.

Nexus-1(config-sync-sp)# no ?
  cdp            Configure CDP parameters
  class-map      Configure a class map
  clock          Clock 
  feature        Command to enable/disable features
  fex            FEX configuration
  hardware       Change hardware usage settings
  interface      Configure interfaces
  ip             Configure IP features
  ipv6           Configure IPv6 features
  lacp           Configure LACP parameters
  logging        Modify message logging facilities
  mac            MAC configuration commands
  mac            MAC
  mvr-config     Enable IGMP MVR
  policy-map     Configure a policy map
  port-channel   Configure port channel parameters
  port-profile   Configure a port-profile
  slot           Configure a slot
  spanning-tree  Spanning Tree Subsystem
  sync-peers     Specify peers to whom configuration needs to be synced
  system         System management commands
  vlan           Vlan commands
  vpc            Vpc
  wrr-queue      Map traffic priority (CoS) values to L3 Multicast Queues


Do I just use conf t and remove the ntp server on both switches?


You can remove the config part and you can disable the NTP feature , that way NTP is not running at all on the Nexus

What do you mean, "remove the config part"?

Do I remove the ntp server x.x.x.x line in both switches or can I do something in config-sync?

We are removing the ntp server command from each switch , and also disabling the ntp feature on each switch

We disabled ntp with the

no ntp feature

command on both switches, and confirmed that ntp is not longer operational, lets hope that will suffice :)

We've done the same thing just to make sure. The NTP feature was disabled and will be enabled after that 1st of July. I'll keep you informed on how things went.

I don't see this version specifically listed.   System version: 5.1(3)N1(1a)

Are we at risk?

Timothy Rothenberg
Cisco Employee
Cisco Employee

Since the leap second bug (CSCub38654) is listed as one of the resolved caveats in release notes for 5.2(1)N1(9), it would seem that 5.2(1)N1(8b) would still susceptible to the advisory.


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