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Interface Flapping: Lost Carrier

      Hi. I just want some advices to troubleshoot an issue that we have with a CISCO2951/K9. It connects to Internet through the GigabitEthernet0/1 interface. Since a few days ago, the Gi0/1 interface is flapping many times in a day:

100468: Oct 30 12:16:28 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down

100469: Oct 30 12:16:29 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down

100474: Oct 30 12:17:08 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up

100475: Oct 30 12:17:09 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up

100468: Oct 30 12:16:28 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
100469: Oct 30 12:16:29 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
100474: Oct 30 12:17:08 CST: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
100475: Oct 30 12:17:09 CST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up

We created an eem applet, that captures the "show clock" and "show interface gi0/1" commands as soon as the interface goes down. These are the results:

Roluter# show interf gi0/1


GigabitEthernet0/1 is down, line protocol is down

  Hardware is PQ3_TSEC, address is 649e.f339.9a01 (bia 649e.f339.9a01)

  Internet address is 192.168.1.75/24

  MTU 1500 bytes, BW 20480 Kbit/sec, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Auto Duplex, Auto Speed, media type is unknown media type

  output flow-control is unsupported, input flow-control is unsupported

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:00:22, output 00:00:02, output hang never

  Last clearing of "show interface" counters 1d15h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 6

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     1330212 packets input, 1339056636 bytes, 0 no buffer

     Received 8648 broadcasts (0 IP multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog, 0 multicast, 0 pause input

     874555 packets output, 104159044 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 unknown protocol drops

     0 babbles, 0 late collision, 0 deferred

    7 lost carrier, 0 no carrier, 0 pause output

     0 output buffer failures, 0 output buffers swapped out

It seems it might be a cable issue, since it is showing "7 lost carrier" and CISCO  says:

no carrierDescription: Cisco IOS sh interfaces counter. The number of times the carrier was not present in the transmission. Common Causes: Check for a bad cable. Check the physical connection on both sides.

Nevertheless, we are managing this router remotely, because it is located at other city; and we don't know how to troubleshoot this issue.

What reasons could be creating the flapping?      Could it be a Internet provider issue?  Could it be the cable on the Gi0/1 interface?  A modem issue?  What is the most common reason to the "lost carrier" log?

Please, we need to solve this problem, and as I said before, we are managing it remotely, so we don't have physical access to it.

Thank you very much.

Fabio

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Interface Flapping: Lost Carrier

what kind of internet connection are y using?

Interface Flapping: Lost Carrier

  I didn't answer earlier, because I was trying to contact someone in order to find out that information. Unfortunately, I haven't received an answer to confirm the kind of internet connection. As far as I know it is cable, (the guaranteed bandwidth is 20 MB). I'm going to try to communicate with the service provider, but I still don't know whether the problem is ours or theirs.

Thanks.

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