Cisco 7604 + RSP720 3CXL + WS-X6704-10GE increasing the error counters on the port, but there is no loss through the port:

   #sh interfaces Te3/4
  TenGigabitEthernet3/4 is up, line protocol is up (connected)
  Hardware is C7600 10Gb 802.3, address is 588d.09b4.8d80 (bia 588d.09b4.8d80)
  MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 42/255, rxload 42/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  1., loopback not set
  Keepalive set (10 sec)
  Full-duplex, 10Gb/s
  Transport mode LAN (10GBASE-R, 10.3125Gb/s)
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 3d03h
  Input queue: 0/75/291/291 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1667291000 bits/sec, 244099 packets/sec
  5 minute output rate 1665910000 bits/sec, 243961 packets/sec
  L2 Switched: ucast: 4875 pkt, 1667250 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 0 pkt, 0 bytes mcast: 0 pkt, 0 bytes
     46982598919 packets input, 40800999530943 bytes, 0 no buffer
     Received 1748682 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     155706 input errors, 65000 CRC, 11401 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     46985469520 packets output, 40792363160570 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

The router is used for the termination of customers and channel limits to them with the using Policing.


#sh int te3/4 transceiver detail
ITU Channel not available (Wavelength not available),
Transceiver is internally calibrated.
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)
---------  -----------------  ----------  ---------  ---------  ---------
Te3/4        28.2                   70.0       60.0        5.0        0.0

                              High Alarm  High Warn  Low Warn   Low Alarm
           Voltage            Threshold   Threshold  Threshold  Threshold
Port       (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
---------  -----------------  ----------  ---------  ---------  ---------
Te3/4        0.00                    N/A        N/A        N/A        N/A

                              High Alarm  High Warn  Low Warn   Low Alarm
           Current            Threshold   Threshold  Threshold  Threshold
Port       (milliamperes)     (mA)        (mA)       (mA)       (mA)
---------  -----------------  ----------  ---------  ---------  ---------
Te3/4         N/A                    N/A        N/A        N/A        N/A

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Te3/4         N/A         ++         0.9        0.4       -8.2       -8.1

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Te3/4         N/A         ++         0.9        0.4      -14.4      -15.0

I'm using an adapter "XENPACK to SFP +" and "Direct Attach Cable SFP + to SFP +" - this complicates the diagnosis.

Where to find the cause of growth counters?

  • 1
    check fiber signal strength, clean fiber terminations (including at patch panels), replace optics.
    – This
    Aug 5 '13 at 13:48
  • I am using direct-attach cable "SFP+ to SFP+" with adapter "XFP to SFP+". Maybe something out of the bunch needs to be replaced. Aug 5 '13 at 15:30
  • Excuse me, I'm using an adapter "XENPACK to SFP +" and "Direct Attach Cable SFP + to SFP +" Aug 6 '13 at 6:37
  • @AllanSundry Excused!
    – jwbensley
    Aug 7 '13 at 13:39

You're seeing CRC and framing errors and general input errors. If this happened while setting up the port this could be caused by people still fiddling with the fiber.

If this happens during normal operation most of the time it indicates a low light level or some other error with the fiber(s) or optics.

You can check the light levels with

show interfaces transceiver 

Beware that this might report incorrect readings for 3rd party optics. You would then have to look up the power budget / limits of the optic to see if you're in range with the specifications.

As Mike suggested, try cleaning all the fiber terminations. If that doesn't help try replacing the optics.

At the moment the errors are too small to be noticed but that can change very quickly. Better fix it now than being woken at 3am because there is suddenly more loss on the line.

Also for interface (error) counters it sometimes pays off to use the Cisco output interpreter to analyse what you're seeing:


Take the analysis with a grain of salt, sometimes they're missing the point but it can help in getting a quick view about what's wrong.


When using a XENPAK/SFP+ Adapter and DAC cables the problem could be with either of them. Try replacing the Adapter(s) and/or cables. As DAC has no optics in it (it's copper), the interface transceiver command will not show anything useful.

Also the cable length and possible electromagnetic interferences could cause problems with DAC. If everything fails try switching to optics and optical cabling and see if that helps.

  • "The Output Interpreter is only available to registered Cisco.com users with a Cisco service contract". Can you give me the article in the as pdf? Aug 5 '13 at 15:29
  • Allan, the .pl CGI that Sebastian linked to doesn't have a PDF copy; that's a tool where you can paste show command output and get recommendations for potential remedies.
    – This
    Aug 6 '13 at 2:52
  • Unfortunately I do not have access to this page. Use of an adapter "XENPACK to SFP +" and "Direct Attach Cable SFP + to SFP +" leads to an empty result of the command "sh int te3 / 4 transceiver detail" (added to the first post). Aug 6 '13 at 6:57
  • Okay, I updated my answer. Aug 6 '13 at 9:56
  • After replacing the DAC to the optical link error counters have stopped growing - in eight hours about 2 input errors. Aug 14 '13 at 6:51

There is loss, you're just not seeing the impact. The display is only showing 155706 input errors out of 46982598919 packets in the previous three days and four hours. This is .0003% packet loss, which is why it's so difficult to see first hand during testing.

If you're not seeing any operational impact, odds are that this can be safely ignored. Such a low level of packet loss has a pretty negligible effect in a standard IP network and the upper-layer protocols will adapt accordingly.

If you're intent on tracking down the source, it will be difficult. As Mike pointed out, the first step will be to check signal strength (show interface xxxx transceiver; this requires modules with DOM capability) and try cleaning the termination points of your patch cords. If that doesn't work, try replacing the patch cords. As a final straw, replace the actual optical modules.


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