A network system according to the present invention includes a plurality of local area networks (LANs); a wide area network (WAN); a plurality of network bridge devices (CPEs) that connect the LANs to the WAN; and a network management apparatus (OSP) that is connected to the WAN and centrally controls the entire network. The LANs and the WAN both comply with the IEEE 802.3 standard. When receiving a MAC broadcast frame (such as DHCP request and ARP request) from the LANs, the CPEs convert it into a MAC unicast frame, and unicast it to the OSP. As a result, bandwidth saturation of the network due to the explosion or concentration of traffic is prevented.
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