Link break detected on Fibre Channel target connected to Brocade switch due to faulty storage end sfp

Applies to

• ONTAP 9
• FCP
• Brocade Switch

Issue

• EMS log on NetApp end reports a link reset event, where the link went down and came back up within 5 seconds.

Wed Feb 14 14:52:15 +0530 [NetApp1: fct_tpd_work_thread_0: scsitarget.slifct.linkBreak:error]: Link break detected on Fibre Channel target HBA 2c with event status 1 , topology type 1, status1 0x0, status2 0x0.
Wed Feb 14 14:52:20 +0530 [NetApp1: fct_tpd_work_thread_0: scsitarget.hwpfct.linkUp:notice]: Link up on Fibre Channel target adapter 2c.

• Tx and Rx power on the storage port are well within the recommended range:

Fibre Channel Target Adapter 2c
Received Optical Power - 996.9 (uWatts)
SFP Transmitted Optical Power - 992.0 (uWatts)

• There are no other FCP events reported on the storage end around the issue time.
• Certain scenorios, where Tx on the lower range:

JxA-NxAxF::> network fcp adapter show -fields sfp-tx-power
node             adapter sfp-tx-power
---------------- ------- --------------
JxA-NxAxFxx02     0e      177.7 (uWatts)

• The connected switch port does not report any errors reported under porterrshow output-

/fabos/cliexec/porterrshow :
          frames        enc     crc     crc     too     too     bad     enc    disc    link    loss    loss    frjt    fbsy     c3timeout     pcs      uncor
        tx       rx      in     err     g_eof   shrt    long    eof     out    c3      fail    sync    sig                      tx      rx      err     err
75:  242.2k  398.3k    0       0       0       0       0       0       0       0       0       0       0       0       0       0       0       0       0

• The state of the switch port is up and online.

/fabos/bin/switchshow :
Index Slot Port Address Media  Speed        State    Proto
============================================================
75    9   11   654bxx   id    N32   Online      FC  F-Port  1 N Port + 1 NPIV public

• Errdump does not have any such erroneous events reported during the issue time.
• Frame timeout detected for the storage connected switch port

2024/09/20-02:37:58, [AN-1014], 434931, FID 128, INFO, Jx_G720_x, Frame timeout detected, tx port 25 rx port 6, sid 3xx00, did 3xx02, timestamp 2024-09-20 02:37:58

• Fabriclog output shows the switch port connected to the affected storage port encountered a reset.

Switch 0; Wed Feb 14 14:51:40 2024 IST (GMT+5:30)
14:51:40.025111 SCN Port Offline;rsn=0x2,g=0x6a             D0,P0  D0,P0  75    NA
14:51:40.025118 *Removing all nodes from port               D0,P0  D0,P0  75    NA
14:51:44.795477 SCN LR_PORT(0);g=0x6a                       D0,P0  D0,P0  75    NA
14:51:44.858285 SCN Port Online; g=0x6a,isolated=0          D0,P0  D0,P1  75    NA
14:51:44.858365 Port Elp engaged                            D0,P1  D0,P0  75    NA
14:51:44.858377 *Removing all nodes from port               D0,P0  D0,P0  75    NA
14:51:44.858608 SCN Port F_PORT                             D0,P1  D0,P0  75    NA
14:51:44.968592 SCN LR_PORT(0);g=0x6a LR_IN                 D0,P0  D0,P0  75    NA

• Sfp Tx power looks very good on the switch end, which tells us that the switch sfp is in a good condition.
• The Rx power is very low ((572.5uW)compared to the Tx power (1238.9 uW) on the switch end.

=============
Slot  9/Port 11:
=============
RX Power:    -2.4    dBm (572.5uW)
TX Power:    0.9     dBm (1238.9 uW)

• Whereas, the storage end Tx power is SFP Transmitted Optical Power - 992.0 (uWatts)
• This tells us that the issue lies somewhere upstream to the switch, which could be the cable or end device sfp ( NetApp storage in this scenario).
• Cable testing needs to be performed to further isolate if the issue is faulty cable.
• If the cable is good, then sfp on end device connected to switch has to be swapped.