Spanning tree control unit in the case of trouble or increase and method thereof

A spanning tree control unit comprising:

• means for making a device transit to a state in which only receiving is conducted in the case of installation of more devices for connecting the network by a plurality of spanning tree protocols or in the case of restarting operation of the devices;
• means for grouping networks by the route discrimination information of the networks in the information in the plurality of networks collected in the state in which only receiving is conducted;
• means for calculating the priority of an own device to satisfy all priorities by which the existing network topology of the grouped networks is not changed;
• and
• means for making the device transit to a state in which sending and receiving can be conducted after the calculated priority has been set in the own device.

A spanning tree control method in a single network of installing more devices by the spanning tree protocol or resuming operation of the devices in the network, comprising the steps of:

• making the devices transit to a state in which only receiving is conducted in the case of installing more devices or resuming the operations;
• collecting information in the network in the state in which only receiving is conducted;
• calculating the priority of an own device, by which the topology of the existing network is not changed, by the collected information;
• and
• making the control unit transit to a sending and receiving possibility state after the calculated priority has been set in the own device.

A spanning tree control method in a plurality of networks of installing more devices for connecting the networks by a plurality of spanning tree protocol or resuming operations of the devices, comprising the steps of:

• making the devices transit to a state in which only receiving is conducted in the case of installing more devices or resuming the operations;
• collecting information in each network in the plurality of networks in the state in which only receiving is conducted;
• grouping each network by route discriminating information of each network collected before;
• calculating the priority of an own device to satisfy all the priorities by which the existing network topology of each network, which has been grouped before, is not changed;
• and
• making the control unit transit to a sending and receiving possible state after the calculated priority has been set in the own device.