host flapping

Discussion in 'Cisco' started by flamer die.spam@hotmail.com, Sep 18, 2008.

  1. flamer

    flamer Guest

    Hi on a cisco 4507 of mine I am getting a lot of these messages:
    %C4K_EBM-4-HOSTFLAPPING Host xx in vlan 1173 is flapping between port
    Gi3/39 and port Po2

    I know it means its seeing the same mac-address from two sources,
    however I am running PVST on all devices, have checked all switches in
    between and STP is forwarding and blocking where appropriate so i see
    no reason for this. no other switches are reporting the same thing
    either. Is there maybe a bug that causes this? its filling up the
    syslog server

    IOS: Catalyst 4000 L3 Switch Software (cat4000-I9S-M), Version
    12.2(20)EW, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)


    Flamer.
    flamer , Sep 18, 2008
    #1
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  2. flamer

    Nicolai Guest

    > Hi on a cisco 4507 of mine I am getting a lot of these messages:
    > %C4K_EBM-4-HOSTFLAPPING Host xx in vlan 1173 is flapping between port
    > Gi3/39 and port Po2
    >
    > I know it means its seeing the same mac-address from two sources,
    > however I am running PVST on all devices, have checked all switches in
    > between and STP is forwarding and blocking where appropriate so i see
    > no reason for this. no other switches are reporting the same thing
    > either. Is there maybe a bug that causes this? its filling up the
    > syslog server


    I had the same on a 4948 - source was a faulty etherchannel to a SUN server.
    (The SUN server announced same mac on the etherchannel and on other nic
    ports)
    Nicolai, Sep 18, 2008
    #2
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  3. flamer

    droidcrasher

    Joined:
    Sep 2, 2011
    Messages:
    1
    Sticky MAC

    If for any reason, you put a port-security setting on a port, and secured it through the MAC, and later moved that machine to another port of the same switch...
    Then your problem may be there...

    As the switch sees the same MAC on two different ports of the same switch, since it is still recorded on the old port (sticky)...and it now sees in on the new one.

    Answer is:

    In global config:
    clear port sticky
    That'll clear all sticky MACs on that switch (if you can't fathom on which port it was!)

    or

    clear port sticky interface (g0/1....for exemple)
    if you know on which port that MAC used to be.

    show run interface
    should show you the recorded MAC on the port.

    Sorry for being late...lol
    I just became a member! :congrats:
    Figured it might help others in the future! :trytofly:
    droidcrasher, Sep 2, 2011
    #3
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