Interface TenGigabitEthernet0/0/11, link down due to MAC local and PHY

[kousik.dutta]

Hi All.

Getting the below alert, can some one help please how to metigate and reason of port flapping.

Interface TenGigabitEthernet0/0/11, link down due to MAC local and PHY line side fault. Transceiver Rx optical power is too low (-40.0 dbm)

[Mark Elsen]

  - @kousik.dutta   On what cisco switch and or device model are you getting this error ?

  M.

[kousik.dutta]

Hi Mark,

Thanks for quick reply. Its C8500-12X

[Mark Elsen]

  - @kousik.dutta      Looks like at times this receiving port the  is essentially getting no usable light signal
                                Check quality of this fiber path first ; with fiber optics testing tools and or hardware 

                               Use the command : show interface TenGigabitEthernet0/0/11 transceiver detail
                               and verify  the warning and alarm threshold optical Tx and Rx power levels for your transceiver

   M.

[MHM Cisco World]

-40 is too low 

Change cable and check

MHM

[Joseph W. Doherty]

As the others have already noted, likely the problem is due to:

Transceiver Rx optical power is too low (-40.0 dbm)

How to mitigate?

Cannot be very specific beyond what the others have already suggested as we don't have specific information on the physical setup.  But, do you perhaps have the other side's received signal strength?  Is it similar and within the expected/desired range?  That might tell us if it's a symmetrical or asymmetrical issue.

If you don't have the tools to test the connection (I'm ignoring the possibility you're using an unsuitable physical setup for the distance), you might try reseating all the fiber connections (possibly after, correctly, cleaning) and/or swapping transceivers.

Otherwise you'll likely need the proper test tools or contract with someone that does.

[pieterh]

to elaborate on "check the cable"

1) you may have used a single mode fiber somewhere in the path while the SFP is multimode
    -> check patch cords on both sides to match the cable interconnecting the sites
    single mode fibre has a smalle diameter then multimode
    and so the SFP receiver only receives light on a small diameter of its sensor
   in this case only approximately 1/50 (1micron diameter SM versus 50 micron diameter MM) of the sensor in the SFP is receiving light, this results in a low optical receive power

2) you may have used a single mode SFP but you are using a multimode fibre cable
    in such case the optical receiver is much smaller than the light beam coming out of the fibre cable
    in this case only approximately 1/50 (1micron diameter SM versus 50 micron diameter MM) of the light energy is received in the SFP

so check the SFP type (MM or SM) match the connecting cable
check the patch cords match the fibre connecting the sites
check the total length match the SFP type (long range / short range)

[Leo Laohoo]

-40.0 dbm is already considered a "cut" where I work.  I'd be on the phone with a fibre tech to bring in his/her OTDR (to determine WHERE the actual break is) and splicer.

[kousik.dutta]

Thank you all for your swift response. I have arrange to replace the SFP.

I will let you know the result as well.

Thanks to all of you again

[kousik.dutta]

This is the output of #sh int Te0/0/1 transceiver

Can you please suggest what is the model of SFP.

Description = SFP or SFP+ optics (type 3)
Transceiver Type: = 10GE SR (27)
Product Identifier (PID) = SFP-10G-SR-S
Vendor Revision = 1.0
Serial Number (SN) = ACW29031H5X
Vendor Name = CISCO-ACCELINK
Vendor OUI (IEEE company ID) = 00.1C.AD (7341)
CLEI code = CMUIAK6CAA
Cisco part number = 10-3105-01
Device State = Enabled.
Date code (yy/mm/dd) = 25/02/19
Connector type = LC.
Encoding = 64B/66B (6)
Nominal bitrate = (10300 Mbits/s)

[Leo Laohoo]

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@kousik.dutta wrote:
Product Identifier (PID) = SFP-10G-SR-S

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If this optic is Cisco-branded, then it is an SFP-10G-SR.

[Mark Elsen]

 - @kousik.dutta                   >...Serial Number (SN) = ACW29031H5X
                                When you enter that serial number in https://cway.cisco.com/sncheck/      you get :
                                Product ID   SFP-10G-SR-S=

                                Replacing the SFP could be done , but if the problem is due to the fiber path and or cable
                                             (a bad in between connection) then that will not help.

  M.

[kousik.dutta]

Thank you Leo.