The OpenFlow protocol is used to discover the nodes and links in a given topology. In a FlowVisor virtualized environment, the FlowVisor controller acts as a proxy between the switch and the controller. Coming to the ports present on the physical switch, FlowVisor edits the OpenFlow message response to indicate only ports that are present in the virtual topology.

Neighbor discovery using the Link Layer Discovery Protocol (LLDP) is unique in a virtualized environment. In a non-virtualized topology (NOX), the controller sends out LLDP messages from its switch ports. Once the messages are received by the switches they are sent back to the controller because they do not match any forwarding rules. With this, the neighbor database is built by NOX. FlowVisor simply intercepts the messages from the controller and tags it with the respective sending slice ID so responses are sent to the right slice once they are received again.