difference between ifOutOctets value and "show int" output errors field on a router - SNMP

This is a discussion on difference between ifOutOctets value and "show int" output errors field on a router - SNMP ; I compare the "output errors" field by running the "show interface" command on a cisco router with the Errors calculated through SNMP by taking the delta of 2 "ifOutOctets" MIB value readings. I find the output errors reading through show ...

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Thread: difference between ifOutOctets value and "show int" output errors field on a router

  1. difference between ifOutOctets value and "show int" output errors field on a router

    I compare the "output errors" field by running the "show interface"
    command on a cisco router with the Errors calculated through SNMP by
    taking the delta of 2 "ifOutOctets" MIB value readings.
    I find the output errors reading through show interface is always very
    much less than the readings of Output errors obtained through SNMP.

    Please could someone explain this huge difference.
    Is show int a valid way of calculating out put errors?
    Any help is appreciated.
    Thanks,
    Jo


  2. Re: difference between ifOutOctets value and "show int" output errors field on a router

    the_rebel_guy@yahoo.com wrote:

    > Please could someone explain this huge difference.
    > Is show int a valid way of calculating out put errors?


    I can't explain the difference. But I know people who trust the CLI
    numbers more than the SNMP numbers... Not sure this is religion or
    hard facts.

    /js

    --
    Juergen Schoenwaelder International University Bremen
    P.O. Box 750 561, 28725 Bremen, Germany

  3. Re: difference between ifOutOctets value and "show int" output errors field on a router


    "Juergen Schoenwaelder" wrote in message
    news:429604a6$0$3463$9b622d9e@news.freenet.de...
    > the_rebel_guy@yahoo.com wrote:
    >
    > > Please could someone explain this huge difference.
    > > Is show int a valid way of calculating out put errors?

    >
    > I can't explain the difference. But I know people who trust the CLI
    > numbers more than the SNMP numbers... Not sure this is religion or
    > hard facts.
    >
    > /js
    >
    > --
    > Juergen Schoenwaelder International University Bremen
    > P.O. Box 750 561, 28725 Bremen,

    Germany

    You can reset the CLI counters, but not the SNMP counters. Perhaps they
    roll over quicker too - but, that doesn't seem as likely.



  4. Re: difference between ifOutOctets value and "show int" output errors field on a router

    Scooby wrote:

    > You can reset the CLI counters, but not the SNMP counters. Perhaps they
    > roll over quicker too - but, that doesn't seem as likely.


    There is no need to reset SNMP counters. You simple read them and then
    you calculate the delta. Note that an SNMP counter does not have a defined
    initial value. Note that this means that every SNMP application which
    reads out a Counter and displays the raw value is actually broken. And
    to really get it right, the application does not only have to compute
    deltas, it also has to check sysUpTime and perhaps some other objects
    to detect counter discontinuities. (And yes, the number of apps that
    get all this really right is unfortunately still small.)

    BTW, the counters that the CLI shows might actually be SNMP counters and
    a reset of the CLI counters perhaps just means that the CLI takes an
    internal snapshot of the SNMP counters and then shows you the deltas.
    Well at least this is what one would expect on boxes where the CLI
    is actually layered on top of the internal SNMP API.

    /js

    --
    Juergen Schoenwaelder International University Bremen
    P.O. Box 750 561, 28725 Bremen, Germany

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