Why are usable hosts less than 2^(32-prefix)?

Network and broadcast were traditionally reserved; many clouds also hold addresses for routers or NAT—check provider docs before assuming every host bit is allocatable.

Can I carve multiple /26 networks inside one /24?

Yes—four /26 blocks fit without overlap if boundaries align. Verify aggregate advertisements and ACL coverage for each slice.

What is a wildcard mask?

Common in Cisco ACLs, it is the bitwise inverse of the subnet mask—translate carefully when copying rules between vendors.

IPv4 Subnet Calculator

CIDR couples an address with a prefix length separating network bits from host bits. From that pair you can enumerate first/last usable hosts, broadcast, and total span—critical for right-sized subnets and non-overlapping VPC peering.

How to use

Enter an IPv4 address and prefix (or classic dotted netmask) from your design template or cloud console.
Read network and broadcast addresses, usable host counts, and whether the provider reserves gateway/metadata slots.
Feed aligned ranges into DHCP scopes, security groups, and infrastructure-as-code modules; document slash notation consistently.

FAQ

Why are usable hosts less than 2^(32-prefix)?: Network and broadcast were traditionally reserved; many clouds also hold addresses for routers or NAT—check provider docs before assuming every host bit is allocatable.
Can I carve multiple /26 networks inside one /24?: Yes—four /26 blocks fit without overlap if boundaries align. Verify aggregate advertisements and ACL coverage for each slice.
What is a wildcard mask?: Common in Cisco ACLs, it is the bitwise inverse of the subnet mask—translate carefully when copying rules between vendors.

IP 子网计算器

输入任意 IPv4 地址与 CIDR 前缀，即刻求出网络掩码、主机网段及广播地址。对齐显示网络位与主机位。

Share Tool & Configuration

You can copy the configuration link of this page or share this tool with your friends.

subnet_inputs.conf

IP 地址 (IPv4 Address)

子网前缀 (CIDR Prefix) /24

# 说明：计算完全由前端 JS 完成，支持 A/B/C 类标准网络和无类别域间路由 (CIDR) 的精确拆分。

subnet_results.log

子网掩码 (Subnet Mask)

255.255.255.0

网络地址 (Network Address)

192.168.1.0

可用 IP 范围 (Usable IP Range)

192.168.1.1 - 192.168.1.254

广播地址 (Broadcast Address)

192.168.1.255

可用主机数 (Total Usable Hosts)

254 个可用 IP 节点 (8 位主机位)

binary_alignment_matrix.bin

💡 图示高亮说明：绿色代表网络号 (Network Bits)；蓝色代表主机号 (Host Bits)。

IP 地址二进制表示 (IP Binary)192.168.1.1

11000000.10101000.00000001.00000001

子网掩码二进制表示 (Mask Binary)255.255.255.0

11111111.11111111.11111111.00000000