IT Tools • 5 min read • January 15, 2024
Understanding Subnet Masks and CIDR Notation
A comprehensive guide to network subnetting and CIDR notation for IT professionals.
What is a Subnet Mask?
A subnet mask is a 32-bit number that divides an IP address into network and host portions. It determines which part of an IP address identifies the network and which part identifies the host.
Understanding CIDR Notation
CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its subnet mask. For example, 192.168.1.0/24 means:
- Network address: 192.168.1.0
- Subnet mask: 255.255.255.0 (24 bits)
- Usable hosts: 254 (192.168.1.1 to 192.168.1.254)
Common Subnet Masks
| /24 | 255.255.255.0 | 254 hosts |
| /16 | 255.255.0.0 | 65,534 hosts |
| /8 | 255.0.0.0 | 16,777,214 hosts |
Practical Applications
Use our IP Subnet Calculator to quickly calculate network addresses, broadcast addresses, and usable host ranges for any subnet.
Pro Tip: When planning networks, always leave room for growth. Use a larger subnet than you currently need.