Subnet Calculator
Calculate network details for any IP address and CIDR prefix
| CIDR | Subnet Mask | Total Addresses | Usable Hosts | Wildcard Mask |
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Frequently Asked Questions
What is a subnet?
A subnet (subnetwork) is a logical subdivision of an IP network. Subnetting divides a large network into smaller, more manageable pieces. Each subnet has a range of IP addresses defined by a network address and a subnet mask. For example, 192.168.1.0/24 defines a subnet with 256 addresses (254 usable hosts) from 192.168.1.1 to 192.168.1.254.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation is a compact way to specify an IP address and its associated subnet mask. It is written as an IP address followed by a slash and a number (e.g., 192.168.1.0/24). The number after the slash represents how many bits of the address are used for the network portion. A /24 means the first 24 bits are the network part, leaving 8 bits (256 addresses) for hosts.
What is the difference between a subnet mask and a wildcard mask?
A subnet mask and a wildcard mask are complementary. The subnet mask identifies the network portion of an address (1 bits = network, 0 bits = host). The wildcard mask is the inverse — it identifies the host portion (0 bits = must match, 1 bits = can vary). For example, a /24 subnet mask is 255.255.255.0 and its wildcard mask is 0.0.0.255. Wildcard masks are commonly used in access control lists (ACLs) and routing protocols like OSPF.
How do I know if an IP address is private or public?
Private IP addresses are reserved for internal networks and are not routable on the public internet. The private ranges defined by RFC 1918 are: 10.0.0.0 to 10.255.255.255 (10.0.0.0/8), 172.16.0.0 to 172.31.255.255 (172.16.0.0/12), and 192.168.0.0 to 192.168.255.255 (192.168.0.0/16). Any address outside these ranges (and not reserved for other special purposes) is a public IP address.