= [http://groups.geni.net/geni/wiki/GENIExperimenter/Tutorials/NFV NFV Tutorial: Managing a Virtual Network Function using SDN and Control Theory] = {{{ #!html
Make sure you have noted the names of the interfaces before you proceed. We will need the interface names to run experiments. (Otherwise, you have to figure out later which OVS interface is connected to each host by pinging from, say, one source to each VNF, after running "sudo tcpdump -i ethX" on each OVS interface.) |
Be careful not to bring down eth0. This is the control interface, if you bring that interface down you won't be able to login to your host. For all interfaces other than eth0 and l0, remove the IP from the interfaces (your interface names may vary). |
An OpenFlow switch will not forward any packet unless instructed by a controller. Basically the forwarding table is empty, until an external controller inserts forwarding rules. The OpenFlow controller communicates with the switch over the control network and it can be anywhere in the Internet as long as it is reachable by the OVS host. |
Standalone vs Secure mode The OpenFlow controller is responsible for setting up all flows on the switch, which means that when the controller is not running there should be no packet switching at all. Depending on the setup of your network, such a behavior might not be desired. It might be best that when the controller is down, the switch should default back to being a learning layer 2 switch. In other circumstances however this might be undesirable. In OVS this is a tunable parameter, called fail-safe-mode which can be set to the following parameters: |