IP Subnet Tool
Calculate IPv4 and IPv6 network boundaries, CIDR prefixes, address capacity and equal subnet divisions. Inspect usable IPv4 hosts, subnet masks, wildcard masks, broadcast addresses, binary breakdowns and interactive allocation visuals, then export subnet data.
| # | Network / CIDR | First usable | Last usable | Addresses |
|---|
Table of Contents
Highlights
- Supports IPv4 and IPv6 addresses with automatic version detection.
- Calculates CIDR ranges, subnet masks and IPv4 usable hosts.
- Splits networks into up to 256 equal subnets.
- Interactive subnet explorer with visual address allocation.
- Exports subnet tables and results as CSV, JSON or TXT.
How IP Subnet Tool Works?
IP subnetting divides an address into a network prefix and the remaining host bits. IPv4 has 32 address bits and IPv6 has 128. A CIDR prefix such as /24 fixes the first 24 bits, leaving eight variable bits in IPv4. The tool accepts an IP address, an optional address/prefix suffix, a prefix field, or an IPv4 dotted subnet mask. A valid dotted mask has contiguous leading ones; when entered, it takes precedence over the prefix field.
Here B is 32 for IPv4 or 128 for IPv6, and p is the CIDR prefix length. The network address is the bitwise AND of the IP address and its mask. The final address sets every host bit to one.
For ordinary IPv4 subnets with at least two host bits, the traditional usable host count excludes the network and broadcast addresses. Under the standard convention, /31 has two usable point-to-point addresses and /32 has one address; the traditional option instead reports zero for both. IPv6 shows the address range without applying IPv4-style broadcast exclusions.
To divide a parent block, choose between zero and eight additional subnet bits, subject to the available host bits. Adding s bits creates 2s equal subnets, each with prefix /(p + s). For example, 192.168.10.42/24 belongs to 192.168.10.0/24; dividing it into four /26 subnets gives 64 addresses per subnet, with 62 traditionally usable hosts.
| IPv4 /26 subnet | Address range | Usable hosts |
|---|---|---|
| 192.168.10.0/26 | 192.168.10.0–192.168.10.63 | 62 |
| 192.168.10.64/26 | 192.168.10.64–192.168.10.127 | 62 |
| 192.168.10.128/26 | 192.168.10.128–192.168.10.191 | 62 |
| 192.168.10.192/26 | 192.168.10.192–192.168.10.255 | 62 |
The results also include IPv4 address class and scope, hexadecimal and binary forms, a usable-versus-reserved IPv4 chart, and an interactive equal-subnet explorer. Subnet rows and summaries can be exported as CSV, JSON or text.
Practical Use Cases
Network administrators: Determine network and broadcast addresses, first and last usable hosts, and subnet masks before assigning static IPv4 addresses or reviewing router interfaces.
IT support technicians: Check whether an endpoint belongs to the expected IPv4 or IPv6 prefix and inspect address scope when investigating connectivity or configuration problems.
Infrastructure architects: Divide an allocated CIDR block into 2, 4, 8 or more equal subnets and compare capacities for different segments.
Cloud engineers: Draft VPC or virtual-network subnet layouts, examine CIDR boundaries and export a preliminary subnet list for review against provider-specific rules.
Networking students: Explore the relationship between prefix length, subnet mask, host bits, binary network boundaries and usable IPv4 host counts using worked examples.
Accuracy and Limitations
Network boundaries and address counts use integer bit operations, including BigInt for 128-bit IPv6 addresses, so supported CIDR calculations are exact. The tool generates only equal-sized splits of up to 256 subnets; it does not perform variable-length subnet planning, routing verification, IP availability checks or live network scans. IPv4 /31 and /32 host counts depend on the selected convention, and address-scope labels are simplified rather than an exhaustive registry classification. IPv6 results show address ranges, not an assigned-host count; cloud platforms may reserve additional addresses.
