| 摘要 |
PROBLEM TO BE SOLVED: To provide: a network system which protects information and prevents illegal access; a relay device; and a method of controlling a network. SOLUTION: A network system 101 includes terminals 6, a DHCP server 3 for managing the IP addresses of the terminals 6 in a network 7 and for dynamically allocating and applying the IP addresses to the terminals 6 in response to a request, and a relay device 10 located between the terminals 6 and the DHCP server 3 to be connected to the network. A plurality of DHCP servers 3a, 3b having different priorities are present in the network 7. The relay device 10 determines a transmission range of a broadcast frame based on an IP address acquisition message exchanged between the terminals 6 and the DHCP servers 3a, 3b, and transmits a response of only the DHCP server 3 that has the highest priority out of the DHCP servers 3a, 3b in responding to an address application server retrieval message from the terminal 6, to the terminal 6. COPYRIGHT: (C)2011,JPO&INPIT
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