Patent ID: 8908566

Claim:
A communication management device that manages data transmission while circulating a token frame indicating a transmission right among communication nodes according to a cyclic order in a group, the group being formed by connecting one communication management device and at least one slave station by an Ethernet® cable in a same network segment, the communication management device comprising: a logical-ring configuring unit that determines a transmission order of the token frame indicating the transmission right and configures a logical ring using the slave station and the communication management device present in a range where the token frame is transmitted by broadcast; a multicast-address generating unit that generates a multicast address from a Media Access Control (MAC) address of the communication management device by modifying a leading bit in the MAC address of the communication management device; a multicast-address storage unit that stores the multicast address; a multicast-address notifying unit that notifies the slave station configuring the logical ring of the multicast address; and a frame-communication processing unit that transmits a frame having a destination address to which the multicast address is set, determines whether the destination address of a received frame coincides with the multicast address stored in the multicast-address storage unit, and switches the frame without performing a receiving process of the frame when the destination address of the received frame does not coincide with the multicast address, wherein the multicast-address generating unit generates the multicast address by: converting the MAC address including the leading bit which is a unique address assigned to the communication management device into a binary form, modifying the leading bit in the binary form in the converted MAC address of the communication management device, converting the converted MAC address including the modified leading bit in the binary form from the binary form back to a hexadecimal form to obtain a modified MAC address, and assigning the modified MAC address of the communication management device as the multicast address for communication in the group.