Rx power low warning; Operating value: -20.7 dBm, Threshold value: -20.0 dBm

[robert]

Hi,

I have installed a new 2960 plus with a original cisco sfp module connected to a 2960S, also with a new cisco sfp, as a trunk.
Curently they are connected with a 2 mtr. fiber cable.

The 2960S keeps logging this information:
Rx power low warning; Operating value: -20.7 dBm, Threshold value: -20.0 dBm

Should I be concerned?

WS-C2960S-48TS-L   15.0(2)SE4            C2960S-UNIVERSALK9-M

sw50-1#sh int gig1/0/52 transceiver
ITU Channel not available (Wavelength not available),
Transceiver is externally calibrated.
If device is externally calibrated, only calibrated values are printed.
++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.
NA or N/A: not applicable, Tx: transmit, Rx: receive.
mA: milliamperes, dBm: decibels (milliwatts).

                                 Optical   Optical
           Temperature  Voltage  Tx Power  Rx Power
Port       (Celsius)    (Volts)  (dBm)     (dBm)
---------  -----------  -------  --------  --------
Gi1/0/52     40.8       3.28      -5.9     -20.6 -

WS-C2960+48TC-L    15.0(2)SE6            C2960-LANBASEK9-M

sw50-2#sh interfaces gig0/2 transceiver
ITU Channel not available (Wavelength not available),
Transceiver is externally calibrated.
If device is externally calibrated, only calibrated values are printed.
++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.
NA or N/A: not applicable, Tx: transmit, Rx: receive.
mA: milliamperes, dBm: decibels (milliwatts).

                                 Optical   Optical
           Temperature  Voltage  Tx Power  Rx Power
Port       (Celsius)    (Volts)  (dBm)     (dBm)
---------  -----------  -------  --------  --------
Gi0/2        41.6       3.30      -6.3     -16.8

regards
Robert

[Mark Malone]

Hi that could be loose cable or dodgy fibre have you tried re-seating them or swapping them out with known working cables , you should  not be constantly seeing alarms like that

[robert]

Thanks for your answers. Currently the 2960 plus is doing nothing until our electrician has installed the fiber cable to the new building where it shall be set in production, so I have only used it for configuration purpose until now without issues.

Currently I only have this one cable.

Robert

[robert]

replaced the fiber cble today, but I still see the log messages from the 2960S switch.

I think, as Reza wrote, it´s nothing to worry about.

[Reza Sharifi]

Hi Robert,

No need to be concern about if your environment is functioning with no issues.  I have seen the same thing on 2960s, 4500x, and ASRs with SFP port.  According to Cisco, this is a cosmetic bug and causes no harm.  If you have SFP ports that are not connected to anything. admin shut the ports. This usually solve the problem with ports that are not connected to anything.

HTH