Calculate IPv4 subnet information, network ranges, and subdivide networks.
Network Information
Network Address
Broadcast Address
Subnet Mask
Wildcard Mask
First Usable Host
Last Usable Host
Total Hosts
Usable Hosts
Additional Details
IP Class
IP Type
CIDR Notation
Binary Subnet Mask
Binary IP
Hex IP
Subnet Division
#
Network
First Host
Last Host
Broadcast
Usable Hosts
What Is Subnetting?
Subnetting is the practice of dividing a network into smaller, more manageable sub-networks (subnets).
It allows network administrators to organize IP addresses efficiently, improve security through
network segmentation, and reduce broadcast traffic. Subnetting is a fundamental concept in networking
that every network engineer, system administrator, and DevOps professional needs to understand.
Key Subnet Concepts
Concept
Description
Example
IP Address
Unique identifier for a device on a network
192.168.1.100
Subnet Mask
Determines which portion of an IP is the network vs host
255.255.255.0
CIDR Notation
Compact representation of subnet mask
/24 = 255.255.255.0
Network Address
First address in the subnet (identifies the network)
192.168.1.0
Broadcast Address
Last address in the subnet (reaches all hosts)
192.168.1.255
Usable Hosts
Total addresses minus network and broadcast
254 hosts for a /24 subnet
Common Subnet Sizes
CIDR
Subnet Mask
Usable Hosts
Typical Use
/32
255.255.255.255
1
Single host (loopback, point-to-point)
/30
255.255.255.252
2
Point-to-point links between routers
/24
255.255.255.0
254
Small office or home network
/16
255.255.0.0
65,534
Large corporate network
/8
255.0.0.0
16,777,214
Major ISP or cloud provider block
Common Use Cases
Network Design: Plan IP address allocation for offices, data centers, and cloud environments.
Cloud Networking: Configure VPC subnets in AWS, Azure, or GCP with appropriate CIDR blocks.
Firewall Rules: Define network-based access controls using CIDR notation.
Troubleshooting: Determine if two IP addresses are on the same subnet to diagnose connectivity issues.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation represents a network address and its subnet mask as
IP/prefix-length. The prefix length is the number of leading 1-bits in the subnet mask.
For example, /24 means 24 bits for the network portion and 8 bits for hosts.
Why can't I use the network and broadcast addresses?
The network address (all host bits = 0) identifies the subnet itself, and the broadcast address
(all host bits = 1) is used to send messages to all devices on the subnet. Neither can be assigned
to an individual host.