Cisco 2950 trunk/access port status up/down every few seconds

[rayeesece4]

hello guys,

I have been facing this issue since couple of days with 2 of my switches. trunk port, access ports changing status to down/up every 5 seconds. not stable.

please can someone point me in right direction.

see the attached log & configuration

thanks.

rayees.

[Leo Laohoo · Accepted solution]

Sound like a layer 1 issue.

What's connected to FastEthernet 0/1?

Can you please post the output to the following command:

• sh interface f0/1
• sh controller e f0/1

[rayeesece4]

Trunk Line connected to fa 0/1 from distribution switch.

it used to work fine but since couple of days i'm noticing this problem.

here are the details requested.

#sh int fa0/1

FastEthernet0/1 is up, line protocol is up (connected)

  Hardware is Fast Ethernet, address is 0015.c6c9.e801 (bia 0015.c6c9.e801)

  Description: TRUSTED PORT TO CAMP3000

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

     reliability 255/255, txload 1/255, rxload 2/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is 100BaseTX

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

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

  Last input 00:00:00, output 00:00:01, output hang never

  Last clearing of "show interface" counters never

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

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 936000 bits/sec, 89 packets/sec

  5 minute output rate 299000 bits/sec, 56 packets/sec

     19165594 packets input, 4189619346 bytes, 0 no buffer

     Received 5099179 broadcasts (0 multicast)

     0 runts, 2 giants, 0 throttles

     309 input errors, 141 CRC, 166 frame, 0 overrun, 9370 ignored

     0 watchdog, 3082231 multicast, 0 pause input

     0 input packets with dribble condition detected

     14358590 packets output, 1598338527 bytes, 0 underruns

     0 output errors, 0 collisions, 2 interface resets

     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

#sh controller e f0/1

  Transmit                                Receive

1603306629 Bytes                       4259017326 Bytes

  14385460 Frames                        19222098 Frames

    153035 Multicast frames                   141 FCS errors

     78044 Broadcast frames               3084363 Multicast frames

         0 Pause frames                   2017125 Broadcast frames

         0 Single defer frames                  0 Control frames

         0 Multiple defer frames                0 Pause frames

         0 1 collision frames                   0 Unknown opcode frames

         0 2-15 collisions                    166 Alignment errors

         0 Late collisions                      0 Length out of range

         0 Excessive collisions               325 Symbol error frames

         0 Total collisions                     1 False carrier errors

         0 Control frames                       0 Valid frames, too small

         0 VLAN discard frames                  0 Valid frames, too large

         0 Too old frames                      20 Invalid frames, too small

  14339071 Tagged frames                        2 Invalid frames, too large

         0 Aborted Tx frames                 9370 Discarded frames

  Transmit and Receive

    227606 Minimum size frames

  15055669 65 to 127 byte frames

   4850733 128 to 255 byte frames

   2243043 256 to 511 byte frames

    991236 512 to 1023 byte frames

   7244491 1024 to 1518 byte frames

   2996190 1519 to 1522 byte frames

[Leo Laohoo]

You have some line errors.  What kind of distro switch do you have?

[Peter Paluch · Accepted solution]

Hello,

I absolutely concur with Leo - this does seem like a physical layer issue.

Sometimes, a good indicator of a problem in cabling or connectors is that after lowering the speed to 10Mbps/Half Duplex by configuration (on both ends of the link, naturally), the line remains stable, however, after allowing it to use higher speeds, it starts flapping again.

Nevertheless, just as Leo suggested, the cabling should be inspected. It may degrade over time, especially if originally not installed entirely properly (e.g. using solid cable in connectors for stranded cable).

Best regards,

Peter

[Leo Laohoo]

Hmmm ... Someone didn't like our answers Pete. 

Must be something I've said. 

[Peter Paluch]

Hi Leo,

Hmmm ... Someone didn't like our answers Pete. 

No, I do not see it that way. I did not suggest anything beyond you've said yourself, and I proposed a rather limited method of identifying a Layer1 fault. So far, it has not been confirmed that it is indeed the case. The rating of "Helpful" is, from this point of view, an appropriate grading.

Best regards,

Peter

[rayeesece4]

Distro is also a 2950.. is it OK to use 2950 as distribution switch or should I use a distro level switch only?  FYI, no reduandant links in network.

I am gonna look at the cabling now, will keep u posted if any luck. thank u leo & peter.

[Leo Laohoo · Accepted solution]

Distro is also a 2950.. is it OK to use 2950 as distribution switch or should I use a distro level switch only?

A 2950 as a distro?  I hope you have a very, very small network.

An ideal "distro" switch would have a minimum of 24-ports of GigabitEthernet.  The "most" Gigabit ports a 2950 can have is two.

Unfortunately, the 2950 does not support TDR.  But my suspicion is that your uplink is faulty.  Could be either one (or both) of the first two pairs are "slipping" from the metal teeth.

[rayeesece4]

Thanks for your help guys, finally I ended up with the faulty trunk cable which was leading to this problem.

Now it seems alrite.

Thaks again for your  quick help & guidence Leo & Peter.

Shaik.

[Leo Laohoo]

Glad to see it's working. 

[Peter Paluch]

Leo,

Glad to see it's working.  

Me too We're good, aren't we? (Just joking... )

Best regards,

Peter

[Leo Laohoo]

lol!

[rayeesece4]

My network is a residential one which has around 250 users, comprising of 10  2950 & 2960 switches, there are few unmanageble switches as well.