A radio bridging device is used for a communications network. If a source host transmits a communications request directed to a destination host, the radio bridging device records an IP address and a MAC address of the source host and an IP address of the destination host in a local table. A state of the source host is set as “LOCAL” if the source host belongs to a segment where the radio bridging device belongs, and set as “AIR” if otherwise. Further, a state of the destination host is set as “SEARCH”, and an ARP request directed to the destination host is broadcast. If an ARP response is received from the destination host, the state of the destination host is changed from “SEARCH” to “LOCAL” or “AIR” to be recorded in the local table together with a MAC address of the destination address.