子网计算工具

根据任意IPv4 CIDR计算网络地址、广播地址、主机范围以及主机数量。

如何使用本工具

1
Type an IPv4 address with a prefix length into the box, for example 192.168.1.0/24. The field is pre-filled with that example to start.
2
Read the results table as you type. The network and broadcast addresses, dotted-decimal subnet mask, first and last usable host, usable host count, and total address count appear immediately.
3
Adjust the prefix length (the number after the slash) to widen or narrow the subnet and watch the host counts change.
4
If you see an Invalid CIDR or Invalid IP message, fix the input. The prefix must be 0 to 32 and each of the four octets must be 0 to 255.

CIDR（无类域间路由）表示法将子网表达为IP/位数；例如，192.168.1.0/24表示前24位用于标识网络，剩余8位（256个地址）用于主机。本工具会计算关于一个子网你需要知道的一切：网络地址、广播地址、可用主机范围以及地址总数。

Sizing a subnet for an office VLAN by checking how many usable hosts a /26 or /25 provides before you assign it.
Finding the network and broadcast addresses you must exclude when configuring a static DHCP address pool.
Translating a CIDR prefix into the dotted-decimal subnet mask a router or firewall interface expects, for example /22 to 255.255.252.0.
Confirming the usable host range when writing an access-control list or firewall rule for a specific subnet.
Verifying that a /31 point-to-point link between two routers gives you exactly two usable addresses with no broadcast waste.
Teaching or studying subnetting for a networking course or a CCNA exam by experimenting with prefixes and seeing host math update live.

/31和/32是什么？▼

/31是一个包含2个地址的子网（点对点链路，无广播）。/32则是单个主机。