On Mar 26, 2008, at 12:58 PM, Gurung, Provin wrote: > 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.
I don't think so, and each ifindex could possibly update at a different time. I've tried sampling at 5 min, 1 min, 30 sec, 10 sec and have definitely seen the accuracy issues outlined below. Dale > --Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of mack > Sent: Tuesday, March 25, 2008 5:42 PM > To: cisco-nsp@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" <[EMAIL PROTECTED]> >> Subject: Re: [c-nsp] SNMP MIB update interval on CISCO? >> To: <cisco-nsp@puck.nether.net> >> Message-ID: <[EMAIL PROTECTED]> >> 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 _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/