Patent ID: 7881292

Claim:
A communication device that carries out a routing operation of data between a first network and a second network, said communication device comprising: a first interface connected to the first network; a second interface connected to the second network; and a processor that assigns an internet protocol (IP) address to a user terminal device connected to the first interface in accordance with a dynamic host configuration protocol (DHCP), wherein the processor changes a first lease period of the IP address set when the processor assigns the IP address to the user terminal device in accordance with the change of a network environment, wherein: the processor evaluates the stability of a connection of a communication between the first interface and the user terminal device and changes the first lease period in accordance with an evaluated result, and when the processor decides that the evaluated result of the stability of the connection of the communication is lower than a prescribed value, the processor sets the first lease period to be shorter than a prescribed period, and when the processor decides that the evaluated result is higher than the prescribed value, the processor sets the first lease period to be longer than the prescribed period.