Nexus PIE report shows "Laser is not enabled" on flapped port

[Petar Rusev]

Hello everyone,

We have two 400G links flapping and I am trying to find a reason why. 

I am trying to understand the meaning of "show pie eventdb link-down-rca detail" report.

What the report says is: 

Reason: Software Bug. Laser is not enabled.
Link Down Reason :Software Bug. Laser is not enabled. 

Do you think it is actual NX-OS SW bug or some QSFP mis-compatibility? 

This report is from 93600CD-GX, running 10.3.3F

[marce1000]

  - You may find this informative  : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwi71532
                                                    although this one won't help
     + Also issue the command Switch# show interface  <interface name> transceiver details
look at the Transmit Fault Count , if available 
     + Look at the interface counters
     + Make sure all connections are solid
     + Check logs on the nexus : preferred = using a syslog server for connecting logs because then you have an easier access
                                                                   to review logging in time
     + Try another SFP('s) if available

    M.

[Petar Rusev]

Thank you for the information marce1000. Do you have any experience with the command suggested in the bug ID? 

I find information about it so far only in the N7K command reference guide:
Cisco Nexus 7000 Series NX-OS Interfaces Command Reference - S Commands [Cisco Nexus 7000 Series Switches] - Cisco

For 9Ks, I was only able to find it in 10.4.x configuration command reference guide, but only in the section New Commands:
Cisco Nexus 9000 Series NX-OS Command Reference (Configuration Commands), Release 10.4(x) - New, Changed, and Deprecated Configuration Commands [Cisco Nexus 9000 Series Switches] - Cisco

I will test it in the lab and share what's the outcome.

[marce1000]

         > Do you have any experience with the command suggested in the bug ID? 
  - No , I am not using the product myself , only doing support ; you may try it :
                   system default link-fail laser-on
    But according to the bug report it doesn't work

     - Personally  I would chose for the upgrade to https://software.cisco.com/download/home/286325342/type/282088129/release/10.3(5)
       (possibly benefiting from other bugfixes and it it an advisory release)

     +  Then check output from show pie eventdb link-down-rca detail
         again and check if the bug condition is still reported (or not)

 M.

[Christopher Hart]

Hi Petar!

I highly recommend opening a case with Cisco's TAC to investigate this issue further if you have not already. It is possible that the root cause of this issue is due to a legitimate software defect - if so, TAC will be able to provide additional details and provide you with the next steps on resolving this issue.

Thank you!

-Christopher

[Petar Rusev]

Hello Christopher,

I was trying to find out everything possible on the Nexus side and also wait on the DWDM provider to check. At the end it was optical attenuator in the optical network which caused the issue.

Nevertheless, I was just about to open TAC because of the Software Bug message. I saved one TAC this time. 

Thank you all for your help.