Mastering Python Networking

The Ryu firewall application

As discussed earlier in the chapter, part of the attraction of OpenFlow is that the technology allows the controller to decide the functions of the switch. In other words, while the switch itself houses the flow, the controller decides the logic of matching fields and the flows to program the switch with. Let's see examples of how we can use the same Mininet topology, but now make the switch behave like a firewall. We will use one of the ready-made sample applications, called rest_firewall.py, as an example. First, we will launch the Mininet network and set the switch version to OpenFlow 1.3:

$ sudo mn --topo single,3 --mac --controller remote --switch ovsk$ sudo ovs-vsctl set bridge s1 protocols=OpenFlow13