how can i use the table 'nas' in the database instead of the clients.conf file

Hello, everybody! I have a lot of clients, whose addresses are 192.168.x.x, 172.x.x.x, ..., every time a new client goes online, i have to configure it in the clients.conf file and what mostly make me sick is i have to restart my radius server again and again. Any body tell how to use the table 'nas' in the database instead of the clients.conf file? Thanks a lot, and have a good weekend.^_^ Kernal Chan