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Cisco Bug: CSCvt97441 - RX power shows -26.98 dBm when remote device TX shows -5.11 dBm

Last Modified

Jul 20, 2020

Products (65)

  • Cisco Nexus 9000 Series Switches
  • Cisco Nexus 3636C-R Switch
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 92348GC-X Switch
  • Cisco Nexus 93600CD-GX Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 9396TX Switch
  • Cisco Nexus 3064 Switch
  • Cisco Nexus 93108TC-FX Switch
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Known Affected Releases

9.3(3)

Description (partial)

Symptom:
Topology :
N9K1 E1/1-----1G fiber link-----E1/1 N9K2

when rx cable removed from E1/1 on N9K1, link will be down after debounce timer expired and the TX laser will be toggled on N9K1 which is expected.
However after the TX laser on N9K1 re-enabled the  RX power on N9K2 shows  -26.98 dBm and link up failed.
we need to know if this is expected behavior and if it is related with 802.3ae.

N9K1
2020 Apr 17 02:59:32.424715 Switch %ETHPORT-5-IF_DOWN_LINK_FAILURE: Interface Ethernet1/1 is down (Link failure)
 
Switch# show int e1/1 transceiver details
Ethernet1/1
    transceiver is present
    type is 1000base-SX
    name is CISCO          
    part number is FTLF8519P3BNL-CS
    revision is A  
    serial number is FNS173628EM    
    nominal bitrate is 1300 MBit/sec
    cisco id is 3
    cisco extended id number is 4
    cisco part number is 10-2626-01
    cisco product id is GLC-SX-MMD         
 
           SFP Detail Diagnostics Information (internal calibration)
  ----------------------------------------------------------------------------
                Current              Alarms                  Warnings
                Measurement     High        Low         High          Low
  ----------------------------------------------------------------------------
  Temperature   35.28 C        90.00 C    -10.00 C     85.00 C       -5.00 C
  Voltage        3.29 V         3.59 V      3.00 V      3.50 V        3.09 V
  Current        6.41 mA       15.00 mA     1.00 mA    12.00 mA       2.00 mA
  Tx Power      -5.11 dBm       0.00 dBm  -13.56 dBm   -3.00 dBm     -9.50 dBm
  Rx Power     -26.98 dBm --    2.99 dBm  -21.54 dBm    0.00 dBm    -16.98 dBm
  Transmit Fault Count = 0
  ----------------------------------------------------------------------------
  Note: ++  high-alarm; +  high-warning; --  low-alarm; -  low-warning
 
N9K2
2020 Apr 17 02:59:42.312164 switch %ETHPORT-5-IF_DOWN_LINK_FAILURE: Interface Ethernet1/1 is down (Link failure)
 
switch# show int e1/1 transceiver details
Ethernet1/1
    transceiver is present
    type is 1000base-SX
   name is CISCO
    part number is SFBR-5716PZ
    revision is 001
    serial number is AGJ1935RB6B
    nominal bitrate is 1300 MBit/sec
    cisco id is 3
    cisco extended id number is 4
    cisco part number is 10-2626-01
    cisco product id is GLC-SX-MMD
    cisco version id is V01
 
           SFP Detail Diagnostics Information (internal calibration)
  ----------------------------------------------------------------------------
                Current              Alarms                  Warnings
                Measurement     High        Low         High          Low
  ----------------------------------------------------------------------------
  Temperature   37.56 C        90.00 C    -10.00 C     85.00 C       -5.00 C
  Voltage        3.31 V         3.63 V      2.97 V      3.47 V        3.14 V
  Current        3.25 mA       12.75 mA     2.00 mA    11.89 mA       2.40 mA
  Tx Power      -5.70 dBm       0.00 dBm  -13.56 dBm   -3.00 dBm     -9.50 dBm
  Rx Power     -26.98 dBm --    2.99 dBm  -21.54 dBm    0.00 dBm    -17.21 dBm
  Transmit Fault Count = 0
  ----------------------------------------------------------------------------
Note: ++  high-alarm; +  high-warning; --  low-alarm; -  low-warning

Conditions:
1G fiber link
when RX cable removed from one side.
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