Break any network into the right subnet.
Enter an IPv4 address and a CIDR prefix to see the subnet mask, network and broadcast addresses, the usable host range, and how many devices the subnet holds.
Your network
Enter a valid IPv4 address, four numbers 0-255 (e.g. 192.168.1.10).
What this means
Subnet breakdown
| Property | Value |
|---|
How subnetting works
What is Subnetting?
Subnetting is the practice of dividing a larger network into smaller, more manageable sub-networks (subnets). Each subnet operates as an independent network segment, improving security, reducing broadcast traffic, and making IP address allocation more efficient. Subnetting is a fundamental skill for network administrators and engineers.
Understanding CIDR Notation
CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length, written as IP/prefix (e.g., 192.168.1.0/24). The prefix indicates how many bits of the address identify the network portion. A /24 means the first 24 bits are the network address, leaving 8 bits (256 addresses) for hosts. Smaller prefixes mean larger networks.
Subnet Masks and Host Calculations
The subnet mask determines which portion of an IP address identifies the network and which identifies the host. A /24 subnet mask is 255.255.255.0, providing 254 usable host addresses (256 total minus the network and broadcast addresses). Understanding the relationship between CIDR prefix, subnet mask, and available hosts is essential for proper network planning.
Common questions
What is the difference between network address and broadcast address?
The network address is the first address in a subnet (all host bits set to 0) and identifies the network itself. The broadcast address is the last address (all host bits set to 1) and is used to send data to all hosts on the subnet. Neither can be assigned to a host device.
How many usable hosts does a /24 subnet have?
A /24 subnet has 256 total addresses (2^8), but 2 are reserved for the network address and broadcast address. This leaves 254 usable host addresses. The formula is 2^(32-CIDR) - 2 for any subnet.
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask, commonly used in access control lists (ACLs) and routing protocols like OSPF. It is calculated by subtracting each octet of the subnet mask from 255. For a /24 subnet mask of 255.255.255.0, the wildcard mask is 0.0.0.255.
What does CIDR stand for?
CIDR stands for Classless Inter-Domain Routing. It replaced the older classful addressing system (Class A, B, C) in 1993, allowing more flexible allocation of IP addresses by using variable-length subnet masking rather than fixed class boundaries.
Reference only. Reserved ranges, provider policies and device firmware may treat edge cases (like /31 point-to-point links) differently.