Child prefixes available
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IPv6 planning
Calculated locally
IPv6 Calculator
Analyze IPv6 prefixes with BigInt-safe math, classify addresses, and preview child subnet ranges without precision loss.
Learn IPv6 addressing and subnetting
Get a practical walkthrough of compression, prefix planning, /64 conventions, and important exceptions.
IPv6 prefix analysis
Enter an IPv6 address with CIDR prefix. Compressed and expanded formats are accepted.
Action
Note: IPv6 has no broadcast address. Neighbor discovery and multicast replace IPv4 broadcast behavior.
IPv6 subnetting mode
Split a parent prefix into child prefixes and inspect a selected index without generating huge lists.
Selected child prefix
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Neighboring child prefixes
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How to use the IPv6 Calculator
Run address analysis first, then use subnet mode to inspect child prefixes by index.
Enter IPv6/CIDR
Use compressed or expanded notation with an explicit prefix length.
Validate structure
Review normalized, expanded, and classification output before deployment.
Plan subnets
Set parent and child prefixes, then select a child index for deterministic addressing.
Copy outputs
Use click-to-copy values for documentation and configuration templates.
IPv6 address structure
IPv6 uses 128-bit addresses, usually shown as eight 16-bit hextets.
Most enterprise designs allocate network hierarchy in the high bits and interface identifiers in the low bits.
IPv6 compression and expansion rules
Leading zeros in each hextet can be omitted, and one longest run of zero hextets can be collapsed with ::.
The calculator always shows both normalized compressed and fully expanded forms to avoid ambiguity.
IPv6 prefix lengths
Common operational prefixes include /48, /56, /60, and /64 depending on site and segment design.
How IPv6 subnetting works
Child prefixes are generated by extending the parent prefix with additional subnet bits.
Example: moving from /56 to /64 adds 8 subnet bits, which creates 256 child /64 prefixes.
Common /48, /56, /60, and /64 designs
Allocate larger blocks to sites and reserve /64 for most LAN and routed interface segments.
IPv6 address types
The calculator identifies global unicast, link-local, unique local, multicast, loopback, unspecified, and documentation ranges.
IPv6 reverse DNS
Reverse mapping uses nibble format under ip6.arpa with hex digits reversed.
IPv6 versus IPv4 subnetting
IPv6 design typically emphasizes consistent prefix lengths and hierarchy over host conservation.
Frequently asked questions
Quick operational answers for common IPv6 planning questions.
Why does IPv6 subnetting use BigInt math here?
IPv6 addresses are 128-bit values. BigInt avoids unsafe precision loss that occurs with standard JavaScript numbers.
Does IPv6 have broadcast addresses?
No. IPv6 uses multicast and neighbor discovery instead of broadcast.
Can I subnet a /48 into /64s?
Yes. That adds 16 subnet bits and yields 65,536 child /64 prefixes.
Related PacketToolbox resources
Use these together for mixed IPv4 and IPv6 planning workflows.
- IPv4 Subnet Calculator for IPv4 masks, wildcards, and host ranges.
- VLSM Planner for variable-length IPv4 subnet design.
- Route Summarization Calculator for clean route advertisements.
- Cisco ACL Builder for access-policy command generation.
- Cisco switch stacking guide for related deployment practices.