IPv6 Subnet Calculator

Published on 2025-11-02 20:40:00 EST last modified 2025-11-02 20:40:00 EST.

Calculate IPv6 subnets, prefixes, and address ranges

Table of Contents

Calculate IPv6 subnets, prefix lengths, and address ranges. Essential for modern network planning and IPv6 deployment.

Calculate IPv6 Subnet

IPv6 Address:

Prefix Length:

Common Use Cases

Network Planning: Design IPv6 address schemes
Subnet Allocation: Divide IPv6 networks for departments/services
Cloud Networking: Plan IPv6 VPC/subnet configurations
Dual Stack: Manage IPv4 and IPv6 networks simultaneously
Address Planning: Allocate addresses for services and devices

Common IPv6 Prefix Lengths

Prefix	Description	Number of /64 Subnets
/32	ISP allocation (minimum)	4,294,967,296
/48	Site allocation (typical)	65,536
/56	Home/small business	256
/64	Single subnet (standard)	1
/128	Single host address	N/A

IPv6 Address Types

Global Unicast (2000::/3)

Public IPv6 addresses
Routable on the internet
Similar to public IPv4 addresses

Link-Local (fe80::/10)

Auto-configured on all interfaces
Not routable beyond local link
Used for neighbor discovery

Unique Local (fc00::/7)

Private addresses (similar to RFC 1918)
Not routable on internet
fd00::/8 used in practice

Multicast (ff00::/8)

One-to-many communication
Replaces IPv4 broadcast

IPv6 Address Format

128 bits divided into 8 groups of 16 bits (hextets)
Written in hexadecimal separated by colons
Leading zeros can be omitted: 2001:0db8 → 2001:db8
Consecutive zero groups can be compressed: :: (only once)

Example:

Lang:

Full:       2001:0db8:0000:0000:0000:0000:0000:0001
Compressed: 2001:db8::1

Important Notes

/64 is the standard subnet size for end networks
Each /64 subnet has 18,446,744,073,709,551,616 addresses
IPv6 has no concept of broadcast addresses
No NAT needed - every device can have a public address
SLAAC (Stateless Address Autoconfiguration) uses /64 prefixes