6500 series ... not populating mac-address table

Discussion in 'Cisco' started by BernieM, Mar 25, 2006.

  1. BernieM

    BernieM Guest

    Our core switch (6513, SUP720, MSFC3) is not creating all the mac-address
    table entries it should be. This is causing traffic to be forwarded out
    other interfaces unnecessarilly.

    The 6513 has a vlan interface for that vlan configured with no ip-address
    but is 'up'. It does create mac-table entries for 'some' hosts in that vlan
    but not all.

    Any ideas where to start looking .. without causing too much 'debug' output.

    BernieM, Mar 25, 2006
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  2. BernieM

    Merv Guest

    What IOS version ?
    Merv, Mar 25, 2006
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  3. BernieM

    BernieM Guest

    Version 12.2(18)SXF3
    BernieM, Mar 25, 2006
  4. BernieM

    Merv Guest

    Do not see any relelvant bugs on CCO.

    Can you describe the situation a little further.

    Is there any pattern to the ports for which the MAC addresses are
    missing ?
    type of module, port position on card, etc, log messages

    Post the output of show vlan x, show bridge x
    Merv, Mar 26, 2006
  5. BernieM

    anybody43 Guest

    Our core switch (6513, SUP720, MSFC3) is not creating all the mac-> > > > address
    Could this be 'by design'?

    The MAC table age time for a VLAN gets set to
    15 seconds for some period if a STP enabled port
    goes up or down unless portfast is configured
    on that port.

    When a VLAN is present on two switches and
    HSRP is in use it is possible that unicast flooding can
    occur. This is now well documented on CCO.

    The fix is basically to set the ARP timeout to
    the mac-address table timeout and to eliminate
    STP TC events by configuring portfast.

    Search CCO for [hsrp unicast flooding]
    You will get many hits.
    anybody43, Mar 26, 2006
  6. BernieM

    BernieM Guest

    Thanks for the reply ... but:

    1) HSRP isn't configured on the switch not populating the mac-table.
    2) It's not a 'timeout', unless it's aging out within 1 sec., as I've
    pinged from one host to another while on the core switch. No mac-table
    entry gets added. No mac-timeouts are set anywhere so they're all 5
    minutes by default.
    3) The ports in question are not bouncing.

    Host access port is standard:

    switcport access vlan x
    switchport mode access
    spanning-tree portfast

    I'll add mode detail ... later. I'm sick now and have just spent the last
    two days in and out of bed.

    BernieM, Mar 26, 2006
  7. BernieM

    Merv Guest

    Are the devices for which the mac-address-table entries are missing
    directly connected to the 6513 in question ?
    Merv, Mar 26, 2006
  8. BernieM

    Merv Guest

    Traffic to the MAC addresses that are not in the mac-address-table
    should be unicast flodded to all ports in the vlan.

    To determine the MAC addresses that are being flooded, you can

    mac-address-table unicast-flood limit <limit in Kpps> vlan <vlan> alert
    Merv, Mar 26, 2006
  9. BernieM

    Merv Guest

    Please post output of

    show vlan <x> ! for the affected vlan

    show spanning-tree <x>

    show bridge <x>

    show mac-address-table vlan <x>

    show module detail
    Merv, Mar 27, 2006
  10. BernieM

    Merv Guest

    Do you have server connected to that vlan using NIC teaming ?
    Merv, Mar 27, 2006
  11. BernieM


    Feb 14, 2008
    Likes Received:
    fixed :)

    I also have had this problem. The above command (well, a variation) has worked great.

    On my 6509: mac-address-table limit vlan [123] action limit flood

    Thanks Merv!
    bearclaire, Feb 14, 2008
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