IPv6 Subnet Calculator
Calculate IPv6 subnets with CIDR notation. Get visual subnet breakdown, address ranges, and network planning information for IPv6 networks.
Common IPv6 Network Examples
💡 IPv6 Subnetting Tips
• Use /64 for LANs: Standard subnet size that supports SLAAC
• Plan hierarchy: Use /48 for sites, /56 for small sites, /64 for subnets
• Don't conserve addresses: IPv6 has abundant address space
• Document your scheme: Keep consistent addressing across your network
• Use ULA for private: fd00::/8 for internal networks
• Standard practices: Follow RFC recommendations for interoperability
🔗 API Access
Integrate IPv6 subnet calculations into your applications with our API:
GET /api/ipv6-subnet?network=2001:db8::/32&prefix=64• Free tier: 200 requests/hour
• API key: 2000 requests/hour, batch calculations
• Documentation: View API Docs
IPv6 Subnetting Basics
IPv6 subnetting is much simpler than IPv4 due to the abundant address space and standardized prefix lengths. Understanding IPv6 subnetting is essential for modern network design.
IPv6 addresses are 128 bits long and use hexadecimal notation with colons. Subnetting uses prefix lengths (like /64) to define network and host portions.
Key Concepts:
- • 128-bit address space (vs 32-bit in IPv4)
- • Hexadecimal notation with colons
- • CIDR notation for subnetting
- • No broadcast addresses needed
- • Standard /64 subnet for LANs
Common IPv6 Prefix Lengths
/48 - Site Prefix
Typically assigned to organizations. Provides 65,536 /64 subnets. Suitable for large enterprises or ISP customers.
/56 - Small Site
Common for residential or small business. Provides 256 /64 subnets. Good balance between flexibility and simplicity.
/64 - Subnet
Standard subnet size for LANs. Required for SLAAC. Provides 18.4 quintillion host addresses.
/128 - Host Route
Single host address. Used for loopback addresses, point-to-point links, or specific host routes.
Frequently Asked Questions
Why use /64 for IPv6 subnets?
/64 is required for SLAAC (automatic address configuration), provides enormous address space, and is the standard recommended by RFC 4291. It simplifies network design by using a consistent subnet size.
How do I plan IPv6 addressing?
Start with your ISP allocation (typically /48 or /56), plan your hierarchy (sites, buildings, floors), allocate /64s for each LAN segment, and document your addressing scheme for consistency.
What about address conservation?
IPv6's vast address space means conservation isn't a concern like IPv4. Focus on clear hierarchy and standard prefix lengths rather than trying to save addresses.
Can I subnet differently than /64?
While possible, avoid subnetting beyond /64 for LANs as it breaks SLAAC. Use /127 or /128 for point-to-point links where SLAAC isn't needed.