IPv6 (Internet Protocol version 6) is the newer standard for routing data across the internet, replacing the older IPv4 protocol. While IPv4 uses 32-bit addresses (supporting about 4.3 billion unique addresses), IPv6 uses 128-bit addresses, enabling approximately 340 undecillion (3.4×10³⁸) possible addresses—enough for the foreseeable future of connected devices.
How IPv6 works
IPv6 addresses are written as 8 groups of hexadecimal digits separated by colons, like 2001:0db8:85a3:0000:0000:8a2e:0370:7334. This can be shortened using zero-compression rules, so 2001:db8:85a3::8a2e:370:7334 is valid. IPv6 uses a simplified 40-byte header (compared to IPv4's variable header), making routing more efficient.
A key feature is Stateless Address Autoconfiguration (SLAAC), which allows devices to self-assign addresses from router advertisements without needing a DHCP server. IPv6 also replaces IPv4's ARP protocol with the Neighbor Discovery Protocol (NDP) for finding neighbors on the same network.
When it matters
IPv6 adoption is critical because IPv4 address exhaustion is real. Any modern infrastructure, application, or DNS configuration should support both IPv4 and IPv6 (dual-stack). DNS lookups return both A records for IPv4 and AAAA records for IPv6.
WarningDual-stack misconfiguration is common: if IPv6 is broken or slow but still "preferred" by your OS, connections may timeout or fall back slowly. Test both protocols actively.