An IP-address distribution device (11; 21; 31; 41) comprising: a path-information obtaining unit (11a; 21a; 31a) that is adapted to obtain a piece of path information indicating a physical connection configuration of a communication network that reaches a terminal (T1, T2, T3, T4; T11, T21, T31) as a request source of an IP address; an IP-address specifying unit (11b; 21b; 31b; 41b) that is adapted to specify an IP address to be distributed to the request source based on a piece of path information of the communication network; and an IP-address correspondence table (11c; 21c; 31c; 41c) adapted to register correspondence relationships between pieces of path information of the communication network and IP addresses, wherein the path-information obtaining unit (11a; 21a; 31a) is adapted to obtain the path information by inquiring a port number of the Ethernet switch (12; 13) that has transmitted a MAC address of the request source, and the IP-address specifying unit (11b; 21b; 31b; 41b), when specifying an IP address-corresponding to the path information of the communication network based on a result of referring to the IP-address correspondence table (11c; 21c; 31c; 41c), is adapted to specify and distribute an IP address, characterized in that said distributed IP address is different from an IP address of a terminal (T1, T2, T3, T4; T11, T21, T31) to which the IP address is already distributed, at a response to an IP address request from a terminal (T1, T2, T3, T4; T11, T21, T31) that is connected to an identical path and has a MAC address different from a MAC address of the terminal (T1, T2, T3, T4; T11, T21, T31) to which the IP address is already distributed. a path-information obtaining unit (11a; 21a; 31a) that is adapted to obtain a piece of path information indicating a physical connection configuration of a communication network that reaches a terminal (T1, T2, T3, T4; T11, T21, T31) as a request source of an IP address; an IP-address specifying unit (11b; 21b; 31b; 41b) that is adapted to specify an IP address to be distributed to the request source based on a piece of path information of the communication network; and an IP-address correspondence table (11c; 21c; 31c; 41c) adapted to register correspondence relationships between pieces of path information of the communication network and IP addresses, wherein the path-information obtaining unit (11a; 21a; 31a) is adapted to obtain the path information by inquiring a port number of the Ethernet switch (12; 13) that has transmitted a MAC address of the request source, and the IP-address specifying unit (11b; 21b; 31b; 41b), when specifying an IP address-corresponding to the path information of the communication network based on a result of referring to the IP-address correspondence table (11c; 21c; 31c; 41c), is adapted to specify and distribute an IP address, characterized in that said distributed IP address is different from an IP address of a terminal (T1, T2, T3, T4; T11, T21, T31) to which the IP address is already distributed, at a response to an IP address request from a terminal (T1, T2, T3, T4; T11, T21, T31) that is connected to an identical path and has a MAC address different from a MAC address of the terminal (T1, T2, T3, T4; T11, T21, T31) to which the IP address is already distributed.