This paper introduces in the detail the applying principles of IP address and MAC address and the methods of subnet division, and analyzes the realization course of the address resolution protocol ( ARP ) and the reverse address resolution protocol ( RARP ). 文章详细地介绍了IP地址、MAC地址的使用原则和子网划分的方法,剖析了地址解析协议ARP和逆地址解析协议RARP的实现过程。