Tuesday, December 1, 2015

Cisco Switch: Checking Optical Power Levels

When you run into poor fiber conditions, you need to prove it so that you can move on instead of banging your head with the customer trying to get you to "make it work".  Below, there is a useful command for that.
Notice the highlighted at the bottom.  On the left side is the actual reading of the optical receive power from the other side.  Notice the low level thresholds though.  Probably enough to cause issues, which it did for me.
2960#show int GigabitEthernet2/0/49 transceiver detail
ITU Channel not available (Wavelength not available),
Transceiver is internally calibrated.
mA: milliamperes, dBm: decibels (milliwatts), NA or N/A: not applicable.
++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.
A2D readouts (if they differ), are reported in parentheses.
The threshold values are calibrated.

                              High Alarm  High Warn  Low Warn   Low Alarm
          Temperature         Threshold   Threshold  Threshold  Threshold
Port       (Celsius)          (Celsius)   (Celsius)  (Celsius)  (Celsius)
--------- ------------------  ----------  ---------  ---------  ---------
Gi2/0/49    35.5                90.0        85.0       -40.0      -45.0

                              High Alarm  High Warn  Low Warn   Low Alarm
           Voltage            Threshold   Threshold  Threshold  Threshold
Port       (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
---------  ---------------    ----------  ---------  ---------  ---------
Gi2/0/49   3.31                  3.63        3.46        3.13       2.97

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi2/0/49    -5.5                -2.7        -3.5        -9.0       -9.9

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi2/0/49   -25.8         -       3.0         0.0       -23.0      -26.0

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