Abstract: A method and an apparatus for monitoring and fault-analyzing a network which includes a plurality of LANs. LAN-to-LAN connectors are provided between LANs. The apparatus includes a monitor fault analyzer. A terminal is connected to a LAN, to issue a command which stores specific packets or transfers stored packets, from a command transmitter to LAN-to-LAN connectors. Upon receiving a command, a command holder of a routing unit (router) of the LAN-to-LAN connector holds the command. The router carries out the usual routing process to pass or block packets transferred from the LAN interfaces according to the addressee. A unit for detecting and copying the specified packets compares the address of each received packet with the addresses stored in the command holder, and if they agree with each other, copies the packet. A data storage unit stores the copy in the storage unit and the time of reception of the packet is measured by the timer and added to the packet.