Terminal affiliation switchover system

A terminal affiliation switchover system that switches over affiliation of a terminal at least between a first network and a second network, the terminal affiliation switchover system comprising:

• a terminal affiliation switchover module that switches over an affiliated network of the terminal between the first network and the second network;
• and
• a DHCP server module that, when the terminal belongs to the first network, allocates an IP address to the terminal based on registry information in a first DHCP table, and when the terminal belongs to the second network, allocates the IP address to the terminal based on registry information in a second DHCP table,
• wherein at every time of any change of the registry information in one of the first DHCP table and the second DHCP table, the DHCP server module makes the change of the registry information reflected in the registry information in the other of the first DHCP table and the second DHCP table, so that the first DHCP table and the second DHCP table have at least identical mapping information representing a correlation of the terminal to the IP address.

A terminal affiliation switchover system that switches over affiliation of a terminal at least between a first network and a second network,

• the terminal affiliation switchover system comprising multiple packet relay devices based on VRRP or virtual router redundancy protocol, wherein the multiple packet relay devices include a first packet relay device set as a master and a second packet relay device set as a backup,
• the first packet relay device as the master having:
• a first terminal affiliation switchover module that switches over an affiliated network of the terminal between the first network and the second network;
• a first DHCP server module that, when the terminal belongs to the first network, allocates an IP address to the terminal based on registry information in a first DHCP table;
• and
• a second DHCP server module that, when the terminal belongs to the second network, allocates the IP address to the terminal based on registry information in a second DHCP table,
• the second packet relay device as the backup having:
• a second terminal affiliation switchover module that, when the second packet relay device is appointed as a new master, switches over the affiliated network of the terminal between the first network and the second network;
• a third DHCP server module that, when the second packet relay device is appointed as the new master and the terminal belongs to the first network, allocates the IP address to the terminal based on registry information in a third DHCP table;
• and
• a fourth DHCP server module that, when the second packet relay device is appointed as the new master and the terminal belongs to the second network, allocates the IP address to the terminal based on registry information in a fourth DHCP table,
• wherein at every time of any change of the registry information in one of the first DHCP table and the second DHCP table, the first DHCP server module and the second DHCP server module in the first packet relay device as the master make the change of the registry information reflected in the registry information in the other of the first DHCP table and the second DHCP table and in the registry information in both the third DHCP table and the fourth DHCP table in the second packet relay device as the backup, so that the first DHCP table and the second DHCP table in the first packet relay device and the third DHCP table and the fourth DHCP table in the second packet relay device have at least identical mapping information representing a correlation of the terminal to the IP address.

A packet relay device that allocates an IP address to a terminal having affiliation switched over at least between a first network and a second network, the packet relay device comprising:

• a first DHCP server module that, when the terminal belongs to the first network, allocates the IP address to the terminal based on registry information in a first DHCP table;
• and
• a second DHCP server module that, when the terminal belongs to the second network, allocates the IP address to the terminal based on registry information in a second DHCP table,
• wherein at every time of any change of the registry information in one of the first DHCP table and the second DHCP table, the first DHCP server module and the second DHCP server module make the change of the registry information reflected in the registry information in the other of the first DHCP table and the second DHCP table, so that the first DHCP table and the second DHCP table have at least identical mapping information representing a correlation of the terminal to the IP address.