Network relay apparatus

A network relay apparatus, comprising:

• a main controller configured to control respective parts of the network relay apparatus;
• a relay processor configured to identify a destination of a packet received via the network interface unit;
• and,
• a network interface unit configured to include:
• a plurality of line interfaces to which physical lines are respectively connected and send and receive a packet to and from outside of the network relay apparatus;
• a data storage configured to store circuit data;
• a programmable logic device by with a logic circuit having a predetermined function is realized ;
• a configuration circuit configured to direct the programmable logic device to configure the logic circuit using the circuit data;
• and
• a state controller provided in a circuit structure other than the programmable logic device to control state of each of the plurality of line interfaces to one of an active state which allows data transmission and reception and a standby state which prohibits data transmission and reception.