Threshold Violation

[davidsbctr]

Getting the following error on a C9500, one port only.

10:10:53.130: %SFF8472-3-THRESHOLD_VIOLATION: Twe1/1/0/19: Rx power low warning; Operating value: -9.2 dBm, Threshold value: -8.0 dBm.

The error registers in the log, every 10 minutes.  

Steps I have taken:

A switch is a C9500 and Z switch is a 4510.

Replaced SFP on both ends.  They are the same type of SFP.

Replaced fiber patch cords on both sides.  MM patch cords.  

Moved connections to a different port, on both ends.

sh int .... transceiver detail shows the optical receive power is too high, no matter which port i move the sfp to.  

[balaji.bandi]

i would asked you to check the cables and SFP matches.

can you post show interface Twe1/1/0/19 trans ( same both the side )

take example if you using  single mode SFP (LRM) you need to use single mode OS2 cable

If the SFO 10G-SR multimode cable ? OM4

how far each device ? how are they connected ?

Other test :

same SFP working on other ports ?

Try to default the port and test it again.

[davidsbctr]

SFPs are the same.

I have links that go farther on this switch and no errors.  This is the only port.  

I've moved the connection to another port on both switches and still getting the error.  So defaulting a port will not help.

Yes, the receive power is too high on twe1/1/0/19.  It was also too high when i had this link connected to twe1/1/0/5.  

[balaji.bandi]

Twe1/1/0/19  connected trunk full 10G SFP-10GBase-LRM    This is the port with the error.

Te5/2  connected trunk full a-10G 10GBase-LRM    This is the Z end and NO errors.  

if the SFP is LRM, you need to use single mode cable OS2

Also if they nearer , make sure minimum 5 meter cable maintained when you using single mode

[MHM Cisco World]

can you share the SFP number ?

[davidsbctr]

Sorry, don't quite understand that question.

Twe1/1/0/19  connected trunk full 10G SFP-10GBase-LRM    This is the port with the error.

Te5/2  connected trunk full a-10G 10GBase-LRM    This is the Z end and NO errors.  

[MHM Cisco World]

length of cable for this SFP 

https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/data_sheet_c78-455693.html

[davidsbctr]

50 Micron MM fiber patch cords.  I have shorter and longer links with the same type of fiber and SFP and this is the only link getting this error.  I have swapped out the SFP on both ends, different patch cords on both ends, and different port on each switch.  I haven't tried to use a fiber pair for the backbone path.  

[mlund]

The receiving signal is too low, the threshold is -8.0 and you are receiving -9,2 that is why you are getting this error. So you have to find out why there is to low signal. Reason for low signal is sfp in other end sending to low, fiberpatch or fiber itself is damaged or dirty, fiber too long. You have tried replacing sfp, swapped patchcables swapped ports. What is left is to clean all connectors with a proper tool for that, or you can try to swap the pairs in the fiber to see if the low value moves to other end.  Do you have an extra pair of fiber, then move the connection to that one. Change the sfp to one with more dB-power

/Mikael

[davidsbctr]

I already swapped SFPs, put in new patch cords, connected to different ports on the switches.  Next possible option is to use different backbone fiber pairs.  Then maybe use SR instead of LRM SFPs.  

[mlund]

Your port complains that there is too low signal with LRM, in one direction. Using different backbone pair is a good way forward, to see if there are problem with actual fiber pair. What have not been told, is, what is the distance of this backbone fiber, and is it single mode or multimode? This will be an important fact when choosing correct sfp. I have not looked in the datasheet, so not sure the distance the sfp will tolerate, but as a rule of thumb (there are exceptions), SR means Short Range over multimode, and LR means Long Range over single mode.