IP Subnet Calculator
Calculate IPv4 and IPv6 subnets with CIDR notation
IP Subnet Calculator
Calculate IPv4 and IPv6 subnets with CIDR notation
IP Subnet Calculator
What is IP Subnetting?
IP subnetting is the process of dividing a larger network into smaller, more manageable sub-networks (subnets). This practice improves network performance, security, and organization.
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by a number to indicate how many bits are used for the network portion of the address.
For example, 192.168.1.0/24 means the first 24 bits represent the network, leaving 8 bits for hosts (256 total addresses, 254 usable).
IPv4 Subnet Reference
Common subnet masks and their CIDR equivalents:
| CIDR | Subnet Mask | Hosts |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 |
| /16 | 255.255.0.0 | 65,534 |
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /30 | 255.255.255.252 | 2 |
Private IP Address Ranges:
• 10.0.0.0/8 (Class A): 10.0.0.0 - 10.255.255.255
• 172.16.0.0/12 (Class B): 172.16.0.0 - 172.31.255.255
• 192.168.0.0/16 (Class C): 192.168.0.0 - 192.168.255.255
IPv6 Subnetting
IPv6 addresses are 128 bits long and use hexadecimal notation:
Standard IPv6 Prefixes:
/48 - Site prefix (usually assigned to organizations)
/56 - Recommended for home networks
/64 - Standard subnet size (most common)
/128 - Single host address
IPv6 Address Types:
• Global Unicast: 2000::/3 - Routable on the internet
• Link-Local: FE80::/10 - Local network segment only
• Unique Local: FC00::/7 - Private addressing
• Loopback: ::1/128 - Equivalent to 127.0.0.1
• Multicast: FF00::/8 - One-to-many communication
IPv6 Benefits:
• Vast address space (340 undecillion addresses)
• No need for NAT in most cases
• Built-in security features
• Simplified network configuration
Network Design Best Practices
Subnet Planning:
Security Considerations: