说明：  IP地址及子网的合法性 使有方法: 程序名 subnet/mask ip_addr 说明:subnet/mask:如211.168.2.0/27 ip_addr: 如211.168.2.3
(IP address and subnet so that the legality of methods: the procedure name subnet/mask ip_addr Description: subnet/mask: such as 211.168.2.0/27 ip_addr: as 211.168.2.3)