In a virtual network apparatus, even when a fault occurs on a private line connecting plural physical network apparatuses to communicate a control signal, the redundancy is maintained, and the lower forwarding capability is prevented. In this network system, a control signal for virtualization to be transmitted and received between plural physical network apparatuses is relayed via a unit spanning LA connecting each physical network apparatus and an adjacent network apparatus in the adjacent network apparatus. Thereby, even when a fault occurs in the private line, it is possible to continue to communicate the control signal between the physical network apparatuses and continuously operate the virtual network apparatus.