[c-nsp] SNMP MIB update interval on CISCO?

[Gurung, Provin]

Thanks for the information. Do the routers maintain a timestamp of when
they last updated their MIB. The time difference between the updates
will give me a good indication of the average traffic being observed by
the router.

Thanks,
-Proveen 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of mack
Sent: Tuesday, March 25, 2008 5:42 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] SNMP MIB update interval on CISCO?

On the 6500/7600 platform you can set:

service counters max age 5

Obviously this is platform specific.
On high CPU load SNMP counters may be updated at a longer interval.
At extreme levels SNMP may stop updating completely until the load goes
down.

Most platforms have a best-effort interval of 10 seconds.

As for the accuracy:

% Accuracy~=update interval*100/sample interval

So with a 60 second sample interval and a ten second update interval
you can have a variance of ~17%.

With a 5 minute sample interval the variance is ~3%.

The accuracy is an approximation as the update interval is best-effort.

To sum it up you can sample slower and get more accurate readings or
faster and
get less accurate readings.

--
LR Mack McBride
Network Administrator
Alpha Red, Inc.


> Message: 9
> Date: Tue, 25 Mar 2008 20:02:23 -0000
> From: "Dean Smith" <dean at eatworms.org.uk>
> Subject: Re: [c-nsp] SNMP MIB update interval on CISCO?
> To: <cisco-nsp at puck.nether.net>
> Message-ID: <005401c88eb3$29605b50$01011bac at thor>
> Content-Type: text/plain;       charset="us-ascii"
>
> Basically - No.
>
> Counters like those are really only valid for polling every minute at
a
> minimum and even then you can occasionally see strange affects due to
> the
> internal updates happening out of sync.
>
> If you essentially need granularity of a second or so sampling you
> probably
> need an external tool.
>
> Dean
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gurung, Provin
> Sent: 25 March 2008 17:02
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] SNMP MIB update interval on CISCO?
>
> I have a question about how to get the cisco routers updates rate of
> one
> of the snmp mib entries.
>
>
>
> Background:
>
>
>
> I am using a cisco 3640 series router running ios 12.4.
>
> I am cyclically doing snmpwalks to get the number of bytes transmitted
> on an output interface for a particular Diff serv code point.  The
> actually snmpwalk call is for cbQosMatchPrePolicyByte
> (enterprises.9.9.166.1.16.1.1.5) in the CISCO-CLASS-BASED-QOS-MIB mib.
>
>
>
> My problem.
>
>
>
> I would like to compute the number of bytes sent per second as quickly
> and accurately as possible.  However I found that the above mib entry
> can be updated anywhere from 6 to 10 seconds.  Sometimes if I poll
this
> snmp entry every 8 seconds the entry hasn't had a chance to change yet
> and my message rate incorrectly is 0 kbs.
>
>
>
> My question:
>
>
>
> 1)      Is there somewhere in the mib or cisco's command line
interface
> where I can get the cyclic rate that is being used? Or the timestamp
> when the MIB entries are being updated?
>
>
>
> 2)      Is it possible to set this rate via snmp or the cisco command
> line interface and make the router update at a fixed interval of my
> choosing?
>
> 3)      Alternatively, Is there a way to generate SNMP traps when
> router
> updates its traffic statistics for some DSCP value?
>
>
>
> Thanks for any inputs,
>
> -Proveen
>
>
>
>
>
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