With the growing usage of the networks, the world-wide Internet has become the main means to exchange data and carry out transactions. It has also become the main means to attack hosts. To solve the security problems which occur in the network such as Internet, we import software products of network security elements like an IDS (Intrusion Detection System) and a firewall. In this paper, we have designed and constructed the general simulation environment of network security model composed of multiple IDSes and a firewall which coordinate by CNP (Contract Net Protocol) for the effective detection of the intrusion. The CNP, the methodology for efficient integration of computer systems on heterogeneous environment such as distributed systems, is essentially a collection of agents, which cooperate to resolve a problem. Command console in the CNP is a manager who controls the execution of agents or a contractee, who performs intrusion detection. In the network security model, each model of simulation environment is hierarchically designed by DEVS(Discrete Event system Specification) formalism. The purpose of this simulation is that the application of rete pattern-matching algorithm speeds up the inference cycle phases of the intrusion detection expert system and we evaluate the characteristics and performance of CNP architecture with rete pattern-matching algorithm.