I found this question how openflow messages get routed from switch to controller? (SDN)

And in the answer it says:

In SDN networks all OpenFlow switches are directly connected to controllers.

But if that's so, then the controller should have many physical interfaces, right? But if I'm not mistaken the controller is a server, and a server does not have so much physical interfaces, right?

So my question is, is the answer to the above question correct? If yes, then how is that physically possible?

1 Answer 1


The quoted answer is not quite correct. Switches have a logical connection to the controller, but not a physical one -- at least not in a network of any size.

Openflow protocol uses TCP/IP (port 6653) like everything else, so some basic routing needs to be in place for switches and controller(s) to communicate.

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