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

[Leslie Clark <lclark@us.ibm.com>]

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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