ITTools

IPv4 Subnet Calculator

Calculate IPv4 subnets, CIDR, network masks, and broadcast addresses.

Network Details

Calculation Results

Network Address

-

Broadcast Address

-

First Usable IP

-

Last Usable IP

-

Usable Hosts

-

Subnet Mask

-

How IPv4 Subnetting Works

Subnetting is the practice of dividing a network into two or more smaller networks. It increases routing efficiency, enhances the security of the network, and reduces the size of the broadcast domain.

What is CIDR Notation?

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing. Instead of using the traditional A, B, and C classes, CIDR uses a suffix like /24 which indicates the number of bits used for the network portion of the address.

Special Cases: /31 and /32

  • /31: Used for point-to-point links. It provides exactly two IP addresses, eliminating the network and broadcast addresses to conserve IP space (RFC 3021).
  • /32: Used to specify a single host. It has exactly 1 usable IP address and is often used in routing tables to point to a specific loopback interface.

Related Tools

What Is My IP

Find your public IPv4 and IPv6 address.

IP Lookup

Find location and ISP data for any IP address.

DNS Lookup

Query DNS records (A, MX, TXT, etc.) for any domain.

Ping

Test the reachability of a host and measure response time.