There are two types of connections on the local computer network (local area network [LAN]) is through a cable (wired) and wereless (wireless). but we don't know with certainy who the user is onnecting to the network. this can threaten network security for users who do not connect the carrying and not easy to trace and find out who did it if there is an any attack. based on security, we needa security system authentication, authorization, and accounting (AAA) to ensure the safety and convenience of users, because with this system we know with certainty who the user is connecting. the user can move from one network to another network, it needed a centralized system. therefore, in this research using RADIUS protocol and focus on the accounting process. accounting results in this study were analyzed and can be used for tracking purpose (who, when, and where and request originated) if there is a crime that uses an internal computer network acess of university of brimawijaya, the process of user aces fees if you use internet acces, as well as materials for planning and resource allocation of bandwidth at the time mendatang.perancangan software includes logical design f computer networks, using a RADIUS server freeradius design, design of database server for storing accounting data, the design of the NAS as a RADIUS client. with this system can be produced with enhanceed security requirements in the form of tracking IP address and time of occurence is known, the value decreased throughput after applying this system that is equal to 5.75%, we can utilaze the results of accountingv data for purposes of calculating the cost of user access to computer networks.