what causes flushes?

Discussion in 'Cisco' started by larry.vaden@gmail.com, Jul 18, 2007.

  1. Guest

    This rural ISP is having problems described below; any help would be
    appreciated.

    Configuration:
    cisco 7206VXR (NPE300) processor with 229376K/65536K bytes of memory
    IOS (tm) 7200 Software (C7200-K4P-M), Version 12.0(32)S6, RELEASE
    SOFTWARE (fc3)

    she-gw#show process cpu | incl utilization
    CPU utilization for five seconds: 68%/46%; one minute: 67%; five
    minutes: 66%

    Issue: poor Miranda (http://miranda.ctd.anl.gov:7123) results from
    customer's viewpoint, including lower downstream rates than upstream
    rates; typically 3% of packets dropped when unix host pings unix host
    on another router interface.

    1st question: should we be concerned about the number of flushes
    below?

    kind regards/ldv

    Larry Vaden
    Internet Texoma, Inc.

    she-gw#show interface Serial3/0 | incl counter
    Last clearing of "show interface" counters 01:00:09
    she-gw#show interface | incl Input queue:
    Input queue: 1/4096/0/51372 (size/max/drops/flushes); Total output
    drops: 0
    ---FE0/0, 18 subnets (secondaries)
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/75/0/22 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/4096/0/0 (size/max/drops/flushes); Total output
    drops: 0
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/75/0/29 (size/max/drops/flushes); Total output drops:
    85
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    Input queue: 0/75/0/2272 (size/max/drops/flushes); Total output
    drops: 0
    Input queue: 24/75/49/107221 (size/max/drops/flushes); Total output
    drops: 0
    ---Serial3/0, upstream DS3
    Input queue: 0/75/0/501 (size/max/drops/flushes); Total output
    drops: 0
    Input queue: 0/75/0/1778 (size/max/drops/flushes); Total output
    drops: 0
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    0
    she-gw
    , Jul 18, 2007
    #1
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  2. <> ha scritto nel messaggio
    news:...
    > This rural ISP is having problems described below; any help would be
    > appreciated.
    >
    > Configuration:
    > cisco 7206VXR (NPE300) processor with 229376K/65536K bytes of memory
    > IOS (tm) 7200 Software (C7200-K4P-M), Version 12.0(32)S6, RELEASE
    > SOFTWARE (fc3)
    >
    > she-gw#show process cpu | incl utilization
    > CPU utilization for five seconds: 68%/46%; one minute: 67%; five
    > minutes: 66%
    >
    > Issue: poor Miranda (http://miranda.ctd.anl.gov:7123) results from
    > customer's viewpoint, including lower downstream rates than upstream
    > rates; typically 3% of packets dropped when unix host pings unix host
    > on another router interface.
    >
    > 1st question: should we be concerned about the number of flushes
    > below?
    >
    > kind regards/ldv
    >
    > Larry Vaden
    > Internet Texoma, Inc.
    >
    > she-gw#show interface Serial3/0 | incl counter
    > Last clearing of "show interface" counters 01:00:09
    > she-gw#show interface | incl Input queue:
    > Input queue: 1/4096/0/51372 (size/max/drops/flushes); Total output
    > drops: 0
    > ---FE0/0, 18 subnets (secondaries)
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/75/0/22 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/4096/0/0 (size/max/drops/flushes); Total output
    > drops: 0
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/75/0/29 (size/max/drops/flushes); Total output drops:
    > 85
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > Input queue: 0/75/0/2272 (size/max/drops/flushes); Total output
    > drops: 0
    > Input queue: 24/75/49/107221 (size/max/drops/flushes); Total output
    > drops: 0
    > ---Serial3/0, upstream DS3
    > Input queue: 0/75/0/501 (size/max/drops/flushes); Total output
    > drops: 0
    > Input queue: 0/75/0/1778 (size/max/drops/flushes); Total output
    > drops: 0
    > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    > 0
    > she-gw
    >


    Hi,

    Flushes generally occur when there is an excessive packet processing for
    your Route Processor. Some "user" packets are to be discarded to let
    priority packets be processed (e.g. control packets ( keepalives, routing
    protocols traffic, other management traffic).
    Sometimes a consistent number of flushed data is associated with some kind
    of DoS attack.

    Note that this protection come in place only with Process Switching; with
    CEF enabled only a small percentage of traffic should be punted to the RP.

    a) Assess why so many packets are process switched
    b) Try and increase your input queue
    c) Upgrade your route processor

    Regards,
    Gabriele
    Gabriele Beltrame, Jul 18, 2007
    #2
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  3. vamsiguturu

    Joined:
    May 28, 2009
    Messages:
    1
    Problem in setting Cisco Aironet Input queue size

    Hi

    Am using Cisco Aironet 1240AG AP.
    I tried to change the input queue size from default(75) to lower size(5).
    I can see the size getting updated when I issue
    --"show interface <my interface> 0".

    But when my TCP Download is going on, when I issue the above command, I never seen the size or drop or flushes getting updated. I always see it as follows :: (0/5/0/0/).
    vamsiguturu, May 28, 2009
    #3
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