How to use Iperf to test the speed on TP-Link routers

Usually, people may want to use Speedtest^® to measure the speed of the router when they encounter the problem that device which connected behind the router has a slower rate or its speed is much slower than the ISP bandwidth.

But the result of Speedtest^® may be affected by the ISP and network delay, so we recommend you use Iperf tool to test. This tool is a little software, and it is convenient to operate. Besides when using Iperf, the host can connect to the server directly, eliminating the effects of the ISP and network congestion, and can measure the most accurate speed, reducing the network influence to the lowest.

This FAQ will tell you how to use Iperf to measure the speed of your TP-Link Router. Before speed measurement, you need to prepare two computers and your Router.

In this topic, We use Load Balance Router TL-R470T+ v6 as an example.

Step 1 Install iperf on computers

1. Before having a test, you may need to install Iperf on both computers, and you can refer to the Iperf official website to download it: https://Iperf.fr/Iperf-download.php
2. The latest version of Iperf is Iperf3, so we used in this FAQ is Iperf3. Please choose the right software version for your computer when download. For example, the system of PC we used in this FAQ is windows64, so we download Iperf3-3.1.3-win64. After downloading, you will get a zip file, extract the zip file; there will be two files --- cygwin1.dll and Iperf3.exe like the following figure showing.

3. Copy these two files to the path C:\Windows\System32, and then the installation is complete.

Step 2 Configure Static IP for PC A and Router

Set up the topology as shown below:

1. In the diagram above, PC A is connected to the WAN port of the router. PC B is connected to the LAN port of the router.

PS:  Please disable the firewall on both computers before testing. The firewall may block test traffic.

2. Set the static IP address of PC A .Set the IP address of PC A as 192.168.2.30.the Subnet mask as 255.255.255.0 and Default gateway as 192.168.2.20.

PS: Due to PC B connect to Router directly, PC B need not configure Static IP address manually, PC B will get the IP address from Router automatically. If you disabled DHCP Server function on Router, please set Static IP address for PC B also.

3. Set the static IP address for WAN port of the Router. Go to the web interface of Router firstly. Usually, the IP address of the router is 192.168.0.1.Choose Network>WAN>WAN1, configure the static IP address for WAN1 port of Router，as shown in the figure:

Step 3 Set Iperf Server and Client to measure the speed of Router

When using Iperf to test the speed, we need to set one PC as a server and another PC as a client, in this FAQ we set PC A as server and PC B as a client.

1. On PC A, press windows key + R; put cmd in the Open bar and click OK; in the cmd dialog box, input the command "Iperf3 -s" and press enter to set PC A as Iperf server.

2. The same operation on PC B to run cmd.exe; in the cmd dialog box, input the command "Iperf3  -c  192.168.2.30", the “-c” means to set PC B as Iperf client, and the IP address behind “-c” is the IP address of the server. After inputting this command, then click Enter to start measuring the speed.

3. As for showing in the above figure, we can see the speed result is 95 Mbps which is around 100Mbps. The TL-R470T+ V6 we used in this FAQ is Fast Ethernet Router. Its NAT throughput is around 100Mbps.

PS: For other TP-Link Gigabit Ethernet Routers, You can find NAT throughput value in Specification of these router.