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Intermittent connections - Interface state UP/DOWN

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  • Intermittent connections - Interface state UP/DOWN

    Hi

    I have a increasingly big problem on my network at work. The network is basically 2 6500s acting as core switches connected to about 25 stacks of 3750s (about 5-7 switches in each stack) which then connect to more than 3000 devices on the network.

    The Problem is that ports on some 4 stacks keep flapping. The users on their PC see the network icon in the bottom right hand corner say "Local area connection disconnected" and the next minute it comes up saying it is connected again. It works for another 2-5 hours before it flaps again.

    On the switch its the same thing...see below (never mind date&time: its not configured on switch:

    How do i fix this????..on one PC i've tried hardcording into full duplex both the port and the pc nic but it still flapped.

    *Sep 24 23:37:24.560: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et1/0/46, changed state to up
    *Sep 24 23:47:08.726: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to down
    *Sep 24 23:47:10.739: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to up
    *Sep 24 23:47:34.898: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/26, changed state to down
    *Sep 24 23:47:35.897: %LINK-3-UPDOWN: Interface FastEthernet4/0/26, changed stat
    e to down
    *Sep 24 23:47:38.162: %LINK-3-UPDOWN: Interface FastEthernet4/0/26, changed stat
    e to up
    *Sep 24 23:47:39.168: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/26, changed state to up
    *Sep 24 23:47:54.444: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to down
    *Sep 24 23:47:56.449: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to up
    *Sep 24 23:48:21.648: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/26, changed state to down
    --More--  *Sep 24 23:48:23.653: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/26, changed state to up
    *Sep 24 23:48:46.185: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to down
    *Sep 24 23:48:47.041: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/44, changed state to down
    *Sep 24 23:48:48.030: %LINK-3-UPDOWN: Interface FastEthernet4/0/44, changed stat
    e to down
    *Sep 24 23:48:48.190: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/47, changed state to up
    *Sep 24 23:48:50.329: %LINK-3-UPDOWN: Interface FastEthernet4/0/44, changed stat
    e to up
    *Sep 24 23:48:51.335: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/44, changed state to up
    *Sep 24 23:48:55.916: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/44, changed state to down
    *Sep 24 23:48:57.921: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et4/0/44, changed state to up
    *Sep 24 23:49:03.583: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et6/0/48, changed state to down
    *Sep 24 23:49:05.588: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern
    et6/0/48, changed state to up

  • #2
    Re: Intermittent connections - Interface state UP/DOWN

    Can you post the config?
    Thank you,

    Marc

    Comment


    • #3
      Re: Intermittent connections - Interface state UP/DOWN

      Hi Dude,

      There may be several reason of this issue .

      1) Sytem lan card problem.
      2) Cabling issue from system to switch.
      3) Dataport of the system or dataport of the switch .
      4) Cable is faulty or loose.


      Proper steps to resolve the issue

      1) Identify how many ports are flapping.
      2) Are all ports are going to one switch
      3) if not identifye the switches and interfaces and check whether u are getting CRC & input error on the interface .
      4) If yes clear it and check if CRC are still increasing or not .If CRC is increasing then check the physical media .
      5) Lastly point out two system on which this problem is occuring and terminsate it directly to the switchport in switch where they are actually terminated .u understand by directly mean direct switch to PC no dataport nothing .
      6) and observe by putting ping of the system.No no drops are occuring then it means ur switchport is fine .then check the physical cabling from your switchport in server room to user seat dataport .

      7) Compare faulty interface config with the nonfaulty interface and see if they are equal or not .


      There are many reason DUDE ,you just need to workout .

      Cheers
      DT

      Comment


      • #4
        Re: Intermittent connections - Interface state UP/DOWN

        well I could put the config here but it would take a very long space. Basically the intermittent connectivity is occuring on 5 out of the 25 stacks that we have. Each of these 5 stacks has from 5-7 3750s each and the dropped connections are occuring randomly on the whole stack which leaves me clueless as to where to begin.

        In response to your advice:

        1. System Lan card problem: I doubt this since all the machines in the organisation are mostly the same model. If this was the case then the problem would spread to the other 20 stacks.

        2. All flapping ports are going to most switches in the stack.

        3. Yes there are CRC and Alignment errors on most flapping ports. After clearing the counter, on one of the flapping ports..alignment errors increased by 8 in 5 hours. At this rate would this cause flapping??..Also one of the flapping ports has no CRC, input or Alignment errors at all.

        4. I will try to make a direct connection from PC to switchport and see if there is any difference. Will update u.

        Now that I've read ur comments, I'm suspecting issues with my patch panels and the cabling.

        Comment


        • #5
          Re: Intermittent connections - Interface state UP/DOWN

          I have had a breakthrough. I had a ccie guy come in to confirm that the wiring in the comms rooms of the stacks with these intermittent connections is not up to scratch.

          Secondly, the model of the PCs that were dropping the connections seemed to have issues with NICs & BIOS.. We have some dell optiplex 755 that were dropping connections. A bios upgrade was pushed through via SCCM and the dropped connections stopped!!!

          All in all its been positive....need to sort out the wiring so my switch logs are clean

          Comment


          • #6
            Re: Intermittent connections - Interface state UP/DOWN

            well thats good that your problem got sort out

            Cheers
            DT

            Comment


            • #7
              Re: Intermittent connections - Interface state UP/DOWN

              I can also share with you some info I've just uncovered, the PC specific intermittent connection issue started after service pack 3 updates....
              .... consequently the bios upgrade fixed it.

              I still have the other intermittent issues caused by the wiring but I'm all happy now and would like to thank you guys!!

              Go Arsenal!!!!!!!!!!!!!!!!

              Comment

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