IPV4地址下有三类内网IP保留地址
A类 Class A 10.0.0.0-10.255.255.255 默认子网掩码:255.0.0.0 B类 Class B 172.16.0.0-172.31.255.255 默认子网掩码:255.240.0.0
C类 Class C 192.168.0.0-192.168.255.255 默认子网掩码:255.255.0.0
