Knowledgebase
Knowledgebase: Windows Support
Network problem diagnostic - Iperf request
Posted by Chris Lewis on Mon 20 April 2015 15:05

To help find any speed irregularities we use a tool called iperf.  This is designed to measure maximum TCP bandwidth, allowing the tuning of various parameters and UDP characteristics. Iperf reports bandwidth, delay jitter, datagram loss.

It is similar to speedtest.net, however speedtest.net has been tweaked to be used with the standard DSL connections for home broadband, and is not completely accurate when used on business grade internet transits, which is why we prefer to use iperf.

The latest version of iperf for your OS can be downloaded from here http://iperf.fr/

Below we show you how to install and use iperf.

 For Windows

  1. Download iperf for Windows from http://iperf.fr/ and extract the contents into C:\iperf (you can also select any location you want for this).
  2. Hold shift and right click on the "iperf" file. Select "open command window here" (see below) This will open up a command prompt into which you can run the iperf commands.

  1. Once open enter the following into the cmd window: iperf.exe -c speedtest.serverspace.co.uk, this performs a basic TCP bandwidth test which measures bandwidth between the client (you) and the iperf server. 

  1. In the same command window, run the command iperf.exe -u -c speedtest.serverspace.co.uk. This runs a UDP test which shows network jitter and any lost datagrams.

 

For Linux

  1. Download and install the iperf application for Linux using the following commands:

 Debian\Ubuntu: sudo apt-get install iperf

 CentOS\Red Hat: yum install iperf

 If you are struggling to install via apt-get/yum installers please do the following to install manually:

  1. wget http://downloads.es.net/pub/iperf/iperf-3.0.6.tar.gz
  2. tar zxvf iperf-3.0.6.tar.gz
  3. cd iperf-3.0.6
  4. ./configure
  5. make
  6. make install
  1. To run a TCP bandwidth test run the following command iperf -c speedtest.serverspace.co.uk, you should see a similar output as below.

  1. To run a UPD test it is the same command but we need to add in the "-u" qualifier". The command for this will be iperf -u -c speedtest.serverspace.co.uk

 Using IPERF in server mode.

 If you need to test a specific connection between, say your location and a server over a vpn connection, you can run iperf with the -s modifier to make it run in server mode, and use the -c modified to connect the client to the server over the network connection you have.

 Once you have the results copy them to us in your support ticket, there should be no problem with pasting the information in like with MTRs as there is little formatting to remove.

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