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Home > Success Center > Network Performance Monitor (NPM) > Calculate interface bandwidth utilization

Calculate interface bandwidth utilization

Table of contents

Updated June 23rd, 2017

Overview

It is sometimes necessary to calculate bandwidth use with SNMP, such as when a customer doesn’t trust NPM’s displayed data.

 

Environment

  • All NPM versions

Steps

 

 

Steps:

  1. Get two SNMP walks from the target device and know the time interval between them,
    • A good starting point is to run the SNMP walks 10 minutes (600 seconds) apart.
    • You can also calculate the difference in sysUpTime (1.3.6.1.2.1.1.3) to get the time delta between the two SNMP walks.
  2. OIDs you need: https://support.solarwinds.com/Success_Center/Network_Performance_Monitor_(NPM)/What_object_IDs_(OIDs)_does_NPM_poll_for_interface_information
    • Select a direction (in or out) and use the 32 or 64 bit counters according to Node setting in NPM (edit node)
    • Select an interface to perform the calculation (more details on next page)
  3. The formula we use to calculate the bps: bps = ((poll2 -poll1)*8)/time_in_seconds_between_polls
  4. How to calculate interface bandwidth and utilization: 

 

 

Example Calculation

  • First find the interface unique ID based on ifName (1.3.6.1.2.1.31.1.1.1.1), ex:
    • .1.3.6.1.2.1.31.1.1.1.1.10 = STRING: “Gigabit Ethernet 1/13“
    • Use the .10 above when searching for the ifInOctets OIDs below
       
  • SNMPWalk1:
    • ifInOctets = 1.3.6.1.2.1.2.2.1.10 = 4061867077
    • ifSpeed = 1.3.6.1.2.1.2.2.1.5 = 1000000000
       
  • SNMPWalk2:
    • ifInOctets = 1.3.6.1.2.1.2.2.1.10 = 158003538 (+ 4294967296 due to counter rollover)
    • ifSpeed = 1.3.6.1.2.1.2.2.1.5 = 1000000000
       
  • Time difference between walks: 793 seconds
     
  • Difference between walk 1 and 2 in ifinoctets: 
    • (158003538 + 4294967296) - 4061867077 = 391103756
       

    391103756 x 8 x 100 = 312883004800
    ----------------------------------------------------
    793 x 1000000000 = 793000000000

 

  • Results = 312883004800 / 793000000000 = 0.3945561220680958
     
  • 0.3945561220680958 x 100 = 39.46% bandwidth IN utilization during the 793 seconds between walks

 

 

 

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