JA Technology Solutions
IPv6 Subnet Calculator
Calculate IPv6 prefixes, expanded and compressed notation, network and host portions, and total addresses.
IPv6 Subnet Calculator
Parse IPv6 addresses in compressed or expanded form, calculate the network prefix, host portion, total addresses, and identify special-use ranges (link-local, unique-local, multicast, loopback). Includes an EUI-64 helper for generating interface identifiers from a MAC address. For IPv4, see the Subnet Calculator.
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Why IPv6 Math Is Different
IPv6 addresses are 128 bits — four times longer than IPv4. They use hexadecimal notation grouped into eight 16-bit blocks separated by colons, with rules that allow leading zeros to be dropped and the longest run of zero blocks to be compressed to ::. A typical /64 subnet contains 18,446,744,073,709,551,616 addresses, so the entire concept of "usable hosts" looks very different from IPv4. Most IPv6 deployments use /64 for end networks because that is the boundary required for stateless address autoconfiguration (SLAAC) and EUI-64.
Special-Use Prefixes
IPv6 reserves specific prefixes for specific purposes: fe80::/10 for link-local, fc00::/7 for unique-local (the IPv6 equivalent of RFC 1918 private addresses), ff00::/8 for multicast, ::1/128 for loopback, and 2000::/3 for global unicast. Understanding which prefix you are working with determines routing, firewall, and addressing decisions.
Migrating to IPv6
IPv6 adoption is no longer optional for organizations operating modern infrastructure — cloud platforms, mobile carriers, and many ISPs now treat dual-stack as the baseline. I help clients design IPv6 addressing plans, evaluate dual-stack vs. NAT64/DNS64 strategies, and audit existing applications for IPv4-only assumptions. Learn about integration services or get in touch to discuss IPv6 migration.
All tools run entirely in your browser. Your data never leaves your machine. Need help? Ask James.