Re: [NV-L] Incorrect bandwidth data above 100MB

[Marcelo Zacchi <mzacchi@gmail.com>]

John and Leslie,

First of all, thanks for your reply!

I think that John's solutions fits me best, because not all the interfaces have their speed set correctly, so that the ifspeed OID is not a good base for BW utilization.

Today I multiply the output from the ifInOctets by 8 to get the values in bits, but if I, instead, multiplied them by 0.008 I would get them in kbits and so forth. 

I will try it first think tomorrow and tell if it works.

Best regards,

Marcelo Zacchi

On Thu, Sep 9, 2010 at 11:18 AM, Leslie Clark <lclark@us.ibm.com> wrote:

The proper formula for interface utilization has always been, in fifth-grade aritmetic:

octets      second          8bits      1
------  *  ---------     *  -----    * ----
second     speed in bits    1octet     100

That is, ((ifInOctets / ifSpeed) * 8)/ 100

Expressed in reverse Polish in mibExpr.conf, that should be

        .1.3.6.1.2.1.2.2.1.10.  \

        .1.3.6.1.2.1.2.2.1.5. / \

        8 * 100 /
That's what it used to be. The last mibExpr.conf that I have in my archives shows it a little different, but the difference would express the % as a whole number (25%) rather than as .25.

BandwidthUtilIn \
"8*100* ifInOctets / ifSpeed" \
        .1.3.6.1.2.1.2.2.1.10.  \

        .1.3.6.1.2.1.2.2.1.5. / \
        800 *

The high speed interfaces need to be polled with SNMPv2 to get the 64bit mib values, and even then they are likely to wrap if you don't poll frequently enough.
I wonder if the devices were discovered using SNMPv1 community strings and are therefore being polled using 32-bit variables?

I've been out of this for a while, so I may be completely wrong.

Cordially,

Leslie A. Clark
IT Services Specialist, Network Mgmt
Information Technology Services Americas
IBM Global Services
(248) 552-4968 Voicemail, Fax, Pager

From:	John M Gatrell <John.Gatrell@uk.ibm.com>
To:	Tivoli NetView Discussions <nv-l@lists.ca.ibm.com>
Date:	09/09/2010 05:23 AM
Subject:	Re: [NV-L] Incorrect bandwidth data above 100MB
Sent by:	nv-l-bounces@lists.ca.ibm.com

---

Yes, I'm seeing something similar. I'm running on AIX NetView 715 Fixpack3.
The graphs did not look right for me when I started monitoring a router with a Gigabit interface and a Bandwidth 200000 (200 Mbit)
statement. The previous router, which had a bandwidth 100000 statement, was graphed correctly.

I'm using an entry in mibExpr.conf namely
BandwidthUtilOut \
"8*100* ifOutOctets / ifSpeed" \
       .1.3.6.1.2.1.2.2.1.16. \
       .1.3.6.1.2.1.2.2.1.5. / \
       800 *

I tried dividing the ifSpeed by 800 first and this gave more believable results.
Your mileage may vary. I tried using:

NewUtilOut \
"ifOutOctets/(ifSpeed/800)" \
       .1.3.6.1.2.1.2.2.1.16. \
       .1.3.6.1.2.1.2.2.1.5. \
       800 / /

John Gatrell

---

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