C6000 MAC aging problem

Discussion in 'Cisco' started by Martin Bilgrav, Dec 1, 2005.

  1. Hi

    I have a wierd problem with MAC aging, which is changed seemingly by it's
    selfs

    The Hardware :

    cisco WS-C6006
    (c6sup2_rp-DSV-M), Version 12.1(26)E4,
    System image file is "slot0:c6sup12-dsv-mz.121-26.E4.bin"


    sho mod, part :

    Mod Ports Card Type Model
    --- ----- -------------------------------------- ------------------
    1 2 Cat 6k sup 1 Enhanced QoS (Active) WS-X6K-SUP1A-2GE
    2 8 8 port 1000mb ethernet WS-X6408-GBIC
    3 24 24 port 100FX Multi mode WS-X6324-100FX-MM
    5 8 8 port 1000mb GBIC Enhanced QoS WS-X6408A-GBIC



    Show running, part :

    mac-address-table aging-time 600
    mac-address-table aging-time 600 vlan 1
    mac-address-table aging-time 600 vlan 10
    mac-address-table aging-time 600 vlan 20
    mac-address-table aging-time 600 vlan 30
    mac-address-table aging-time 600 vlan 40


    When I continuely issue the command, I see that the aging time flops back
    and forth between the configured 600 sec and 15 sec !!

    #show mac-address-table aging-time
    Vlan Aging Time
    ---- ----------
    Global 600
    1 600
    10 15
    20 600
    30 600
    40 600


    #show mac-address-table aging-time
    Vlan Aging Time
    ---- ----------
    Global 600
    1 600
    10 15
    20 15
    30 600
    40 600

    #show mac-address-table aging-time
    Vlan Aging Time
    ---- ----------
    Global 600
    1 600
    10 600
    20 600
    30 600
    40 600

    #show mac-address-table aging-time
    Vlan Aging Time
    ---- ----------
    Global 600
    1 600
    10 15
    20 600
    30 600
    40 600


    and so on ...

    What can cause this ?
    Are there any protocols etc, that can "tell" the C6000 to fx. negotiate the
    timer settings, or change it ?


    HELP !
    Martin
     
    Martin Bilgrav, Dec 1, 2005
    #1
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  2. The CAM aging timer is dropped to 15 seconds by STP when a port changes
    state. This can cause major issues on a busy network with ports changing
    states at short intervals, as it will effectively cause flooding of an
    entire VLAN with unicast traffic. This issue can be minimised by configuring
    spanning tree portfast on all device end ports (i.e. those connected to
    PC's, servers, printers, etc. rather than to other switches/hubs), as this
    stops the change in port state triggering STP topology change notifications.

    BL
     
    Buzz Lightbeer, Dec 1, 2005
    #2
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  3. notifications.

    Thank you, Buzz, for such a nice and quick reply.
    I will go ahead and verify these settings.

    Martin
     
    Martin Bilgrav, Dec 2, 2005
    #3
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