Testing Network Conditions with WANem: A Free WAN Emulator

When preparing for a new internal project, I encountered the need to simulate various networking conditions and scenarios. Specifically, I wanted to test how our vCenter Client would perform over high latency satellite links with varying bandwidth availability and even packet loss scenarios. To do this, I turned to WANem, a free WAN emulator that allows me to control the various networking characteristics in a controlled environment.

WANem is a virtual appliance that can be run as a VMware virtual machine. Setup is straightforward, and I won’t go into detailed instructions here. If you’re interested in learning more about how to set up WANem, I may write a HOWTO post in the future.

Once WANem is set up and running in your network environment, all you need to do is route your traffic through it. In my test environment, I decided to route all traffic between my local computer and my vCenter Server through the WANem appliance. This is easily done by opening a command prompt with administrator privileges on your local computer and using the following command:

route add {destination IP} mask 255.255.255.255 {WANem IP}

Where {destination IP} is the IP address of the server or application you want to test, and {WANem IP} is the IP address of the WANem appliance.

To tune the network properties of the traffic going through WANem, I opened the WANem admin page in my browser and made some adjustments. The screenshots below show the advanced tab:

As a simple test, I added 500ms latency (delay time) and a packet loss of 25%. This allowed me to simulate the effects of high latency and packet loss on our vCenter Client.

WANem is a great tool for testing how your applications and networking infrastructure will perform under adverse network conditions. It’s free, easy to use, and can be set up in a variety of networking environments. If you need to test the robustness of your network and applications, WANem is definitely worth checking out.

Note: The information in this blog post is based on my own experience with WANem, and should not be taken as expert advice. Always consult with a qualified IT professional before making any changes to your networking environment.