Mininet SDN Lab Environment with Custom Python Topologies

I built reproducible SDN test environments with the Mininet Python API, defining custom multi-switch topologies that spin up on demand against a remote controller. Codifying topologies made OpenFlow and controller experiments repeatable and disposable.

Objective & Context

Mininet emulates real networks with lightweight namespaces and Open vSwitch, so an entire fabric runs on one host. This lab uses the Python API to script topologies, providing the reproducible substrate for the SDN concepts, OpenFlow, and controller labs.

Environment & Prerequisites

• Mininet with Open vSwitch; Python 3.
• A remote controller (Ryu/ONOS) for non-trivial topologies.
• Root privileges (Mininet manipulates namespaces).

Step-by-Step Execution

1. Define a topology with the Python API

from mininet.topo import Topo
class TwoSwitch(Topo):
    def build(self):
        s1, s2 = self.addSwitch('s1'), self.addSwitch('s2')
        self.addLink(s1, s2)
        self.addLink(self.addHost('h1'), s1)
        self.addLink(self.addHost('h2'), s2)
topos = {'two': (lambda: TwoSwitch())}

2. Launch against a remote controller [PRIVILEGED]

3. Validate full reachability

*** Results: 0% dropped (2/2 received)

Validation & Testing

Run pingall and iperf within the emulated topology to confirm connectivity and link behaviour. Pass criteria: 0% drop with the controller present and a clean teardown via mn -c.

Key Results

• Scripted reproducible multi-switch topologies that deploy in seconds.
• Provided the disposable substrate for 3 dependent SDN labs.
• Achieved 0% packet drop in controller-managed reachability tests.
• Standardized clean teardown to prevent cross-run contamination.