CIDR IP Subnet & Network Security Range Calculator
Calculate IPv4 subnet masks, CIDR network address, broadcast, usable host ranges, and firewall rules in real time.
Subnet Network Properties
Mastering IPv4 Subnetting & CIDR Notation
In computer networking, an IP subnet partitions a physical network into smaller, logical subnetworks. This improves network performance by isolating broadcast traffic and enforces perimeter security policies between internal departments (e.g. DMZ, database servers, and public web servers).
The prefix length (such as /24) represents how many bits of the 32-bit IPv4 address are allocated to the network prefix. The remaining bits ($32 - 24 = 8$ bits) address the individual host interfaces ($2^8 = 256$ addresses).
Frequently Asked Questions
What are RFC 1918 Private IP Ranges?
RFC 1918 defines three non-routable private ranges reserved for local intranets: 10.0.0.0/8 (16.7M hosts), 172.16.0.0/12 (1M hosts), and 192.168.0.0/16 (65,536 hosts).
What is the difference between /31 and /32 subnets?
A /32 represents a single host address. A /31 (RFC 3021) provides 2 IP addresses and is specifically used for point-to-point router links without network and broadcast address overhead.