The present invention relates to a service method for a construction of networks having automatic
backup and load-balancing upon failures to networks and systems, and more particularly to a dedicated
private network service method having a load-balancing function wherein the network
backup is available since a bypass path is made to normally operating IDC centers upon failures to a specific IDC of the IDCs dispersed in plural places in a public IP networks by GLB servers, and load-balancing as to entire servers is available by constructing network equipment changeable into a
private IP network in case of connecting to the IDC centers, connecting the network equipment by
Giga lines, and using dispersed IDCs as a network constructed in one place. Further, the present invention, in a dedicated
private network, comprises steps of (1) performing a bypass connection to an IDC normally operated upon a failure of a specific IDC by connecting a user by IDC center in a public IP network by a GLB
server upon a user's connection; (2) changing a public
IP address to a
private IP address upon a connection to the dedicated
private network; (3) load-balancing traffic to plural IDC centers after interactively connecting the respective IDC centers by constructing a ring-shape network with the IDC centers of
private IP networks connected by
Giga lines; and (4) performing the load balancing of servers by identifying
server states at SLB servers in the respective IDC centers.