How to see frag/defrag utilization of the router.

Discussion in 'Cisco' started by AM, Nov 25, 2005.

  1. AM

    AM Guest

    I would know how to see whether the router is busy on
    defragmentin/fragmenting of packets about wrong settings of MTU.
    I have IPsec traffic going through the router and when it is present the CPU
    blasts up to 100%. Every other traffic can reach peaks of 400-500 kbytes per
    second while the IPsec traffic only 30/40 kBytes per second.
    Using "cpu show proc" the sum of all processes is close to 1% while the
    percentage on the top of list reaches 95/100%.

    Many thanks,

    Alex.
     
    AM, Nov 25, 2005
    #1
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  2. AM

    Igor Mamuzic Guest

    Hi,

    You can use 'show ip traffic' command to check for frags/defrags among the
    other things... 'debug ip traffic' is also valuable, but limit it with ACL
    or use it at low utilization day periods...

    When 'sh proc cpu' indicates high cpu percentage, but sum of all processes
    does not reach that cpu percentage (in your case 95/100%) then this means
    that your cpu is busy because of high number of interrupts.
    Make sure that your router has CEF switching enabled: 'show ip int' and then
    look for the "IP CEF switching is enabled" or similar.
    Next, if you suspect IPSec traffic for this issue, check if your router is
    equipped with AIM-VPN card or it's on board variant and if so, type 'sh
    crypto engine accelerator statistic' to check if AIM-VPN card is making it's
    purpose.
    If all from the above is ok, then consult the following URL:
    http://www.cisco.com/en/US/products/ps6350/prod_tech_notes_list.html
    and look for "Troubleshooting high CPU utilization" links...

    B.R.
    Igor






    "AM" <> wrote in message
    news:eek:RGhf.6202$...
    >I would know how to see whether the router is busy on
    > defragmentin/fragmenting of packets about wrong settings of MTU.
    > I have IPsec traffic going through the router and when it is present the
    > CPU
    > blasts up to 100%. Every other traffic can reach peaks of 400-500 kbytes
    > per
    > second while the IPsec traffic only 30/40 kBytes per second.
    > Using "cpu show proc" the sum of all processes is close to 1% while the
    > percentage on the top of list reaches 95/100%.
    >
    > Many thanks,
    >
    > Alex.
    >
    >
     
    Igor Mamuzic, Nov 26, 2005
    #2
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  3. AM

    Hansang Bae Guest

    AM wrote:

    > I would know how to see whether the router is busy on
    > defragmentin/fragmenting of packets about wrong settings of MTU.
    > I have IPsec traffic going through the router and when it is present
    > the CPU blasts up to 100%. Every other traffic can reach peaks of
    > 400-500 kbytes per second while the IPsec traffic only 30/40 kBytes
    > per second. Using "cpu show proc" the sum of all processes is close
    > to 1% while the percentage on the top of list reaches 95/100%.



    Is your IPSec traffic going through serial interfaces? If so, just
    crank the physical mtu to 1600 on both side. "sho ip traffic" will
    tell you how many packets you are fragmenting.

    --

    hsb


    "Somehow I imagined this experience would be more rewarding" Calvin
    **************************ROT13 MY ADDRESS*************************
    Due to the volume of email that I receive, I may not not be able to
    reply to emails sent to my account. Please post a followup instead.
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    Hansang Bae, Nov 26, 2005
    #3
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