Let's say we have an existing SDN network composed of several switches and a controller. Now say we connected a new switch to the network. Now how would the new switch know how to reach the controller? And how did the first switches know how to reach the controller in the first place?
The only way I can think of is there must be some routing protocol running on the switches. But if they are running a routing protocol, wouldn't that violate the concept of SDN? Because in SDN, we are removing the control plane from the switches and place it on the controller, and if switches are running a routing protocol then they still have their control plane functioning.
Please enlighten me.