Testing SDN behavior with Mininet
Mininet lets you test new controller features for your software-defined network in a sandbox before releasing them onto your production network.
With a simple software update for the OpenFlow controller, a network admin can often change the entire behavior of an OpenFlow-based network . You can even write the update yourself – after all, most controllers are available under open source licenses – but how do you find out whether your controller extension harmonizes with the topology of the production network? It would be too bad if you enabled your changes and the routing or the firewall went rogue. If you want to test the update extensively in a controlled environment first, you will turn to Mininet  sooner or later.
Sandbox for Network Admins
Mininet describes itself as "An instant virtual network on your laptop (or other PC)." With Mininet, you only need a single Linux system to emulate a network that deploys hundreds of virtual switches and hosts. Mininet can thus emulate a complete network with connected computers on a single machine; the host hardware decides the maximum number of switches and virtual hosts you can use. With an OpenFlow controller, you can then control this test network at will, and the emulated hosts will run any unmodified Linux program. Therefore, you can use Mininet to check whether and how the changed network affects individual programs running on it.
Mininet doesn't just test routing and forwarding rules. If you want to change the topology of a real network, you can simulate the consequences in advance using Mininet, or you can use Mininet to evaluate new networks in the planning phase.
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