输入 IPv4 地址并选择 CIDR 前缀，立刻得到网络地址、广播地址、子网掩码、通配符掩码、可用主机范围和地址数量——配网络、划分网段、排查地址冲突都用得上。Enter an IPv4 address and pick a CIDR prefix to instantly get the network address, broadcast address, subnet mask, wildcard mask, usable host range and address counts — for network planning and troubleshooting.
可用主机数按传统规则（总数 −2，扣掉网络地址和广播地址）计算；/31 点对点链路（RFC 3021）和 /32 主机路由按现代惯例不扣减。私有地址段：10.0.0.0/8、172.16.0.0/12、192.168.0.0/16。Usable hosts follow the classic rule (total − 2 for the network and broadcast addresses); /31 point-to-point links (RFC 3021) and /32 host routes are not reduced. Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.