IPv4 CIDR Address Blocks
Please select a block of IP addresses below to view the IPv4 CIDR subnet mask range and related neighborhood IP address listings. This includes all listings from 1.0.0.0/8 to 255.0.0.0/8.
What is an IP Address Subnet?
An IP Address Subnet, also known as a "subnetwork", is the efficient allocation of an IP network in blocks of IP addresses. Class A Blocks end with "/8" and contain 16 million IP addresses. Class B Blocks end with "/16" and contain 65,000 IP addresses. Class C Blocks end with "/24" and support a maximum of 254 IP addresses.
- Class A Example - 1.1.1.0/8 - 16 Million Hosts
- Class B Example - 1.1.1.0/16 - 65,000 Hosts
- Class C Example - 1.1.1.0/24 - 254 Hosts
What is CIDR notation?
CIDR format, or "Classless Inter-Domain Routing", released in 1993, is the industry standard for displaying IP addresses and their related subnets. It consists of a network prefix and the significant bits which determines the size of the IP block. Significant bits are in 8-bit groups that form Class A, B, and C blocks of IP addresses. An example of CIDR format is "255.254.0.0/16", which indicates there are 65,000 hosts in this range from "255.254.0.1" to "255.254.255.255".
