Patent ID: 7813303

Claim:
A network fault detection apparatus, which detects faults in a network including a plurality of nodes including a plurality of terminals and a plurality of relay devices, and also including an L3 bridge connection, the network fault detection apparatus comprising: a communication unit receiving first packets as replies from a first node corresponding to a first network address among the plurality of nodes, and receiving second packets as replies from a second node corresponding to a second network address among the plurality of nodes; and a detection unit for detecting an L2 loop by the L3 bridge connection which causes a network fault when determining that any of the first packets includes a first source physical address which is also included in any of the second packets, and a second source physical address which is not included in any of the second packets, and any of the second packets includes a third source physical address which is also included in any of the first packets, and a fourth source physical address which is not included in any of the first packets.