Rx power high warning

[mtmharison]

Hi,

I have an Rx power high warning message in my router.

can I leave my router running with this message as it's just a warning or should I install an attenuator because in the long run the router will be damaged?

I use multimode fiber and SFP

Regards,

[Marvin Rhoads · Accepted solution]

The underlying problem should be addressed. or it will eventually cause the SFP to fail prematurely.

In my experience however that's a very unusual situation for a multimode fiber connection. Usually the transmit power isn't such that it will over-run a receiver.

Can you share the output of "show interface transceiver detail" for the affected interface?

[mtmharison]

i was wrong, I use a monomode SFP and fiber

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)
--------- ------------------  ----------  ---------  ---------  ---------
Gi1/0/25    27.3                89.0        85.0        -5.0       -9.0

                              High Alarm  High Warn  Low Warn   Low Alarm
           Voltage            Threshold   Threshold  Threshold  Threshold
Port       (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
---------  ---------------    ----------  ---------  ---------  ---------
Gi1/0/25   3.29                  3.60        3.50        3.10       3.00

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi1/0/25    -5.6                 1.0        -3.0        -9.5      -13.5

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi1/0/25    -0.2         +       1.0        -3.0       -19.0      -23.0

[Marvin Rhoads · Accepted solution]

Ah OK, that's more normal to see with singlemode.

From the output, you are in the "warning" and not "alarm" range so it is relatively safe to continue operating like that. If it were my network and that was an important link , I'd put a 5 dB optical attenuator inline.

If you're US-based.,m you can pick one up via Amazon for US$5.99.

https://www.amazon.com/Fiber-Attenuator-Singlemode-Simplex-Fixed/dp/B001B1HOOM

[Joseph W. Doherty]

I recall (?) asking Cisco about this, and was told, physical damage isn't likely but the receiver could "misread" an overpowered RX.

Normally, as Marvin notes, this isn't an issue on low powered optics. What kind of SPF? What's the fiber cable length?

[mtmharison]

I use an 1000BaseLX GLC-LH-SMD SFP with 2 meters of fiber

[Joseph W. Doherty]

2 meters is often quoted as a minimum, but I'm unable to find real confirmation via standards.

If you can obtain an attenuator, for $6 dollars, I would seriously consider Marvin's suggestion to install one. That would seem an inexpensive way to get your power level within spec.

[mtmharison]

it's ok

thanks everybody

[jijijiji20016]

this isn't an issue on low powered optics. What kind of SPF? What's the fiber cable length?

[Carl Lindahl]

I have seen this on 10G SR SFPs facing a 40G QSFP Break out on a short run Multimode, and ended up buying 3 db MM attenutators surprisingly.

[R T]

I got the high alarms issue on the 10Gbase-SR, that is connecting to the FPGA.... Somehow the port was disconnected unexpectedly....

# sh int e1/12 transceiver details
Ethernet1/12
transceiver is present
type is 10Gbase-SR
name is CISCO-AVAGO
part number is SFBR-709SMZ-CS1
revision is G4.1
serial number is AVD24179015
nominal bitrate is 10300 MBit/sec
Link length supported for 50/125um OM2 fiber is 82 m
Link length supported for 62.5/125um fiber is 26 m
Link length supported for 50/125um OM3 fiber is 300 m
cisco id is 3
cisco extended id number is 4
cisco part number is 10-2415-03
cisco product id is SFP-10G-SR
cisco vendor id is V03

SFP Detail Diagnostics Information (internal calibration)
----------------------------------------------------------------------------
Current Alarms Warnings
Measurement High Low High Low
----------------------------------------------------------------------------
Temperature 45.40 C 75.00 C -5.00 C 70.00 C 0.00 C
Voltage 3.22 V 3.63 V 2.97 V 3.46 V 3.13 V
Current 8.15 mA 10.50 mA 2.50 mA 10.50 mA 2.50 mA
Tx Power -2.51 dBm 1.69 dBm -11.30 dBm -1.30 dBm -7.30 dBm
Rx Power -0.60 dBm + 1.99 dBm -13.97 dBm -1.00 dBm -9.91 dBm
Transmit Fault Count = 0
----------------------------------------------------------------------------
Note: ++ high-alarm; + high-warning; -- low-alarm; - low-warning