1

Sometimes gigabit port starts blinking amber light and when i do sh int count err i can see how "RCV err" growth.

SW-Floor-2#show int gig 2/0/27 counters err

Port        Align-Err     FCS-Err    Xmit-Err     Rcv-Err  UnderSize  OutDiscards
Gi2/0/27            0           1           0       10134          0            0

Port      Single-Col  Multi-Col   Late-Col  Excess-Col  Carri-Sen      Runts     Giants
Gi2/0/27           0          0          0           0          0          0          0

And sometimes interface shuts down and goes up automatically on other side.

Here my logs:

W-Floor-2#sh log
Syslog logging: enabled (0 messages dropped, 1 messages rate-limited, 0 flushes, 0 overruns, xml disabled, filtering disabled)

No Active Message Discriminator.



No Inactive Message Discriminator.


    Console logging: level debugging, 95104 messages logged, xml disabled,
                     filtering disabled
    Monitor logging: level debugging, 329 messages logged, xml disabled,
                     filtering disabled
    Buffer logging:  level debugging, 95104 messages logged, xml disabled,
                    filtering disabled
    Exception Logging: size (4096 bytes)
    Count and timestamp logging messages: disabled
    File logging: disabled
    Persistent logging: disabled

No active filter modules.

    Trap logging: level informational, 92800 message lines logged
        Logging Source-Interface:       VRF Name:

Log Buffer (4096 bytes):
.0 dBm. (SW-Floor-2-3)
Nov 28 21:20:34: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low warning; Operating value: -18.9 dBm, Threshold value: -17.0 dBm.
Nov 28 21:24:13: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.3 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 21:24:15: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.3 dBm, Threshold value: -19.0 dBm.
Nov 28 21:28:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0/51, changed state to down
Nov 28 21:28:42: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0/51, changed state to up
Nov 28 21:30:34: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-3)
Nov 28 21:30:36: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm.
Nov 28 21:32:40: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/8, changed state to down
Nov 28 21:32:41: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/8, changed state to down
Nov 28 21:34:15: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.5 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 21:34:17: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.5 dBm, Threshold value: -19.0 dBm.
Nov 28 21:40:37: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-3)
Nov 28 21:40:39: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm.
Nov 28 21:44:17: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 21:44:19: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm.
Nov 28 21:47:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0/3, changed state to down
Nov 28 21:47:55: %LINK-3-UPDOWN: Interface GigabitEthernet3/0/3, changed state to down
Nov 28 21:47:58: %LINK-3-UPDOWN: Interface GigabitEthernet3/0/3, changed state to up
Nov 28 21:47:59: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0/3, changed state to up
Nov 28 21:50:39: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -20.0 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-3)
Nov 28 21:50:41: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -20.0 dBm, Threshold value: -19.0 dBm.
Nov 28 21:54:19: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 21:54:21: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm.
Nov 28 22:00:41: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -20.0 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-3)
Nov 28 22:00:43: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -20.0 dBm, Threshold value: -19.0 dBm.
Nov 28 22:04:21: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.6 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 22:04:23: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.6 dBm, Threshold value: -19.0 dBm.
Nov 28 22:10:43: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-3)
Nov 28 22:10:45: %SFF8472-5-THRESHOLD_VIOLATION: Gi3/0/51: Rx power low alarm; Operating value: -19.4 dBm, Threshold value: -19.0 dBm.
Nov 28 22:14:23: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm. (SW-Floor-2-2)
Nov 28 22:14:25: %SFF8472-5-THRESHOLD_VIOLATION: Gi2/0/27: Rx power low alarm; Operating value: -19.8 dBm, Threshold value: -19.0 dBm.





SW-Floor-2#show controllers ethernet-controller gig 1/0/27

     Transmit GigabitEthernet1/0/27           Receive
   3079381646 Bytes                       1150071762 Bytes
    169736103 Unicast frames               157574604 Unicast frames
      3325069 Multicast frames                513275 Multicast frames
       939914 Broadcast frames                258543 Broadcast frames
            0 Too old frames               313695412 Unicast bytes
            0 Deferred frames               79832894 Multicast bytes
            0 MTU exceeded frames           29254751 Broadcast bytes
            0 1 collision frames                   0 Alignment errors
            0 2 collision frames                  82 FCS errors
            0 3 collision frames                   0 Oversize frames
            0 4 collision frames                   0 Undersize frames
            0 5 collision frames                  19 Collision fragments
            0 6 collision frames
            0 7 collision frames               24108 Minimum size frames
            0 8 collision frames            54768642 65 to 127 byte frames
            0 9 collision frames            50404995 128 to 255 byte frames
            0 10 collision frames            5592659 256 to 511 byte frames
            0 11 collision frames            3267416 512 to 1023 byte frames
            0 12 collision frames           44348443 1024 to 1518 byte frames
            0 13 collision frames                  0 Overrun frames
            0 14 collision frames                  0 Pause frames
            0 15 collision frames
            0 Excessive collisions             89236 Symbol error frames
            0 Late collisions                    251 Invalid frames, too large
            0 VLAN discard frames              29197 Valid frames, too large
            0 Excess defer frames                 48 Invalid frames, too small
       114355 64 byte frames                       0 Valid frames, too small
     46406323 127 byte frames
     48216664 255 byte frames                      0 Too old frames
      5748932 511 byte frames                      0 Valid oversize frames
      3592061 1023 byte frames                     0 System FCS error frames
     69828220 1518 byte frames                     0 RxPortFifoFull drop frame
        94531 Too large frames
            0 Good (1 coll) frames
            0 Good (>1 coll) frames

I checked duplexes on both sides and its set full-duplex. I changed patch cords, changed SFP modules and problem still occuring.

Please help.

Sorry for my english.

0
1

You don't have enough power. If you have replaced the SFPs and patch cords, you need to try different horizontal fibers. You may have bad fiber terminations on the fiber patch panel. I would get a cable vendor in there to run some tests on the fiber and correct any problem found. They will have the proper test equipment.

Always start troubleshooting at layer-1.

1

The received power levels on ports Gi2/0/27 and Gi3/0/51 are simply too low for reliable transmission. As Ron's already pointed out this is a layer-1 problem. When the power budget is exceeded you need to either increase the budget or lower attenuation.

Power loss/attenuation can be caused by:

  • excessive length
  • unsuitable fiber type
  • bad splices
  • dirty or damaged fiber connectors
  • fiber bend radius below tolerance
  • defective transceivers
  • single-mode/multi-mode fiber type mismatch
  • bad/missing mode conditioning
  • APC/SPC end face mismatch
  • unsuitable PHY for fiber type/length

Also check the opposite direction fiber/far side port for the same problems, indicating a general problem (length, systematic mismatches) as opposed to port-specific problems (dirt, damage).

If you can rule out all those - especially the potential mismatches - you can select a PHY type with a higher power budget that might be able to handle the attenuation of the fiber. E.g. instead of 1000BASE-LX(10) you could use -EX or -ZX. For more specific information you'll need to add details about the used fiber type, length, and SFP types to your question.

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