Netzwerk
IPv4 Subnet Calculator
The subnet calculator takes an IP address and subnet mask in CIDR notation and computes all relevant subnet details: network address, broadcast address, first and last usable host addresses, subnet mask, wildcard mask, and the number of available hosts. It also supports splitting a larger subnet into smaller ones. It is an essential daily tool for network engineers, cloud architects, and sysadmins.
What is a Subnet Calculator?
A subnet calculator computes the properties of an IP subnet defined by an IP address and a prefix length (CIDR notation) or a dotted-decimal subnet mask. Given an input like 192.168.1.45/26, it determines the network address (the base address of the subnet), the broadcast address (the last address), the range of usable host addresses, the subnet mask in dotted-decimal form, the wildcard mask (bitwise inverse of the subnet mask), and the total number of hosts. This eliminates the need to perform binary subnet calculations by hand.
How does it work?
Enter an IP address with a CIDR prefix (e.g., 10.0.0.100/22) or an IP address and separate subnet mask. The tool converts both to 32-bit integers, applies a bitwise AND to find the network address, applies a bitwise OR with the inverted mask to find the broadcast address, and derives all other values. Class-based address detection (Class A, B, C) and private address range identification are also shown. A subnet split feature allows dividing the result into equal smaller subnets.
Typical Use Cases
- Planning IP address allocation for a corporate or cloud network
- Configuring firewall rules that reference network blocks
- Verifying subnetting calculations in network certification study
- Designing VPC subnets for AWS, Azure, or GCP cloud environments
Step-by-step Guide
- Step 1: Enter an IP address with CIDR prefix (e.g., 192.168.10.0/24).
- Step 2: Click Calculate to compute all subnet properties.
- Step 3: Review the network address, broadcast, host range, and host count.
- Step 4: Use the subnet split feature if you need to divide the range into smaller blocks.
Example
Input
192.168.1.0/26
Output
Network: 192.168.1.0, Broadcast: 192.168.1.63, Hosts: 192.168.1.1–192.168.1.62 (62 usable)
Tips & Notes
- A /24 gives 254 usable hosts, a /25 gives 126, a /26 gives 62 — each step halves the host count.
- The wildcard mask is used in Cisco ACLs and OSPF area statements — it is the bitwise inverse of the subnet mask.
- When allocating cloud subnets (AWS VPC), remember that cloud providers reserve additional addresses beyond network and broadcast.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its associated prefix length as a single string (e.g., 10.0.0.0/8). The prefix length is the number of consecutive 1-bits in the subnet mask, indicating how many bits are used for the network portion.
How many hosts does a /27 subnet support?
A /27 subnet has 32 addresses total (2^(32-27) = 32). Subtracting the network address and broadcast address leaves 30 usable host addresses.
IPv4 Subnet Calculator
Calculate all details for an IPv4 CIDR block: network address, subnet mask, broadcast address, usable hosts, binary representation, and subnet splitting.
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