Address Aging Issue

Discussion in 'Cisco' started by Dan, Jan 21, 2004.

  1. Dan

    Dan Guest

    Is anyone familiar with the address aging issue between a Catalyst 1900
    and a Catalyst 2900. Specifically, if a laptop is disconnected for a
    1900 port to a 2900, the use can't login to the network. The work
    around is too go into the 1900's Address Aging field and change it from
    18000 to 300 and the wait 5 minutes and laptop can connect. Then change
    the aging back to 18000. Here is what firmware/ios is running:

    1900 Firmware v 7.02

    2900 V 11.2(8.6)sa6

    Is there a way to fix this issue as it is very annoying.

    TIA, Dan
     
    Dan, Jan 21, 2004
    #1
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  2. Why do you change the aging time back? The important thing is to have the same
    aging time on all your switches in the network. 18000 seems a bit too high for
    me. I would suggest something like 30 minutes.

    Regards,
    Christoph Gartmann

    --
    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Immunbiologie
    Postfach 1169 Internet: [email protected] dot mpg dot de
    D-79011 Freiburg, Germany
    http://www.immunbio.mpg.de/home/menue.html
     
    Christoph Gartmann, Jan 21, 2004
    #2
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  3. Dan

    Dan Guest

    I think 1800 seconds (300 minutes) was the default. But even changing
    it to 30 minutes is not going to fix the problem will it if done on all
    3 routers?. I don't know how to change the Address Aging on the 2900 as
    it has a command line which commands i am not too familiar with.

    Also, what about upgrading the firmware in the 1900s and IOS in the 2900?

    TIA, Dan
     
    Dan, Jan 22, 2004
    #3
  4. Dan

    AnyBody43 Guest


    This may not be 100% but I think that it is not too bad.

    The original solution to this behviour (I don't think that it is a
    'problem') is to relay on the Spanning Tree Protocol
    which is enabled by default.

    STP sent (note past tense) a Topology Change Notification (TCN)
    whenever a port was brought up or went down (I think both).

    This caused the forwarding database (terminology from 802.1d,
    sorry) to be put into fast aging which is, IIRC, 15 seconds.

    I cannot now recall exactly but I suspect that ports with
    portfast enabled do not result in TCN on state change.

    Anyway to your issue, the default aging time is 300s and
    unless there was a sepcific problem being experienced
    I see no need to change it.

    If you have STP off you could consider turning it on which
    would enable fast aging.

    I do not have time right now to look up the portfast vs
    fast aging thing.

    Finally remember that 802.1d protocol was designed
    when there was the real prospect of a 2000 node (or more)
    bridged network and processors were less fast and memory was
    much more costly. Modern stuff is really (perhaps I should
    say Absolutely) fabulous in comparison. It would be most unusual
    consider increasing the aging time from the default.

    Good luck.
     
    AnyBody43, Jan 22, 2004
    #4
  5. I just noticed: 1800 seconds is already 30 minutes. So try something like
    300 (5 minutes). At least there shouldn't be a problem when moving a computer
    if you wait 30 or five minutes before reconnecting it.
    Connect to it, then at the prompt:
    ...
    # configure terminal
    (config)# interface ethernet 0
    (config-if)# arp timeout 300
    (config-if)# end
    (config)# end
    # write mem
    Not a bad idea either.

    Regards,
    Christoph Gartmann

    --
    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Immunbiologie
    Postfach 1169 Internet: [email protected] dot mpg dot de
    D-79011 Freiburg, Germany
    http://www.immunbio.mpg.de/home/menue.html
     
    Christoph Gartmann, Jan 22, 2004
    #5
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