A protocol for discovering a silent device, such as a printer, attached to a mobile port of a switching node. A command is transmitted to the switching node for associating an IP address for the silent device to a particular virtual local area network (VLAN). Entry of the command causes the switching node to start searching for the silent device on the mobile ports. As part of the searching process, an ARP request with the IP address provided in the command is sent to each mobile port of the switching node. When the silent device responds with its MAC address in an ARP reply message, the MAC address is learned in a layer 2 table used for making forwarding decisions of data units received by the switching node. Furthermore, the port where the silent device was discovered, that is, the port receiving the ARP reply message, is associated with the VLAN of the silent device.