对Sniffer软件的功能和使用作了介绍，讲述了利用工具软件解决问题的思路和一些分析方法。对IP协议，ARP协议，PPPOE协议，Radius的解码做了详解-Sniffer software on the function and use were presented about the use of tools to solve the problem of thinking and some analysis. On the IP protocol, ARP protocol, PPPOE