A network access system for performing access to a data center constituted by a plurality of real servers (RS1-RS5), from a client terminal via a network, comprising: a domain name server adapted to report access identification information of any one of the plurality of real servers (RS1-RS5) on the basis of an access request message from the client terminal, to the client terminal; and a plurality of load balancers (LB1-B3) adapted to allocate a connection with the client terminal on the basis of the access request message from the client terminal including the access identification information specified by the domain name server, characterised in that each of the plurality of load balancers (LB1-LB3) is adapted to execute: processing for determining a real server (RS1-RS5) to be connected by a first access request message including the access identification information from the client terminal; processing for generating server identification information for the determined real server (RS1-RS5) and encoding the generated server identification information which can be decoded by using key information shared between the plurality of load balancers (LB1-LB3); processing for adding the encoded server identification information to the access identification information; processing for achieving connection from the client terminal to the determined real server (RS1-RS5) by sending the access request message to the determined real server (RS1-RS5); processing for upon receiving, from the client terminal, a second access request message based on the access identification information to which the encoded server identification information has been added, after a response message including the encoded server identification information has been sent back to the client terminal from the determined real server (RS1-RS5) via the network; processing for reading out the encoded server identification information from the access identification information in the second access request message and decoding the encoded server identification information by using the key information shared between the plurality of load balancers (LB1-LB3); and processing for sending the access request message to the real server (RS1-RS5) identified by using the decoded server identification information. a domain name server adapted to report access identification information of any one of the plurality of real servers (RS1-RS5) on the basis of an access request message from the client terminal, to the client terminal; and a plurality of load balancers (LB1-B3) adapted to allocate a connection with the client terminal on the basis of the access request message from the client terminal including the access identification information specified by the domain name server, processing for determining a real server (RS1-RS5) to be connected by a first access request message including the access identification information from the client terminal; processing for generating server identification information for the determined real server (RS1-RS5) and encoding the generated server identification information which can be decoded by using key information shared between the plurality of load balancers (LB1-LB3); processing for adding the encoded server identification information to the access identification information; processing for achieving connection from the client terminal to the determined real server (RS1-RS5) by sending the access request message to the determined real server (RS1-RS5); processing for upon receiving, from the client terminal, a second access request message based on the access identification information to which the encoded server identification information has been added, after a response message including the encoded server identification information has been sent back to the client terminal from the determined real server (RS1-RS5) via the network; processing for reading out the encoded server identification information from the access identification information in the second access request message and decoding the encoded server identification information by using the key information shared between the plurality of load balancers (LB1-LB3); and processing for sending the access request message to the real server (RS1-RS5) identified by using the decoded server identification information.