What is IPv6?

IPv6 (Internet Protocol version 6) is a network-layer protocol standardized in RFC 2460 (1998) that replaces IPv4. Its primary innovation is a 128-bit address field, yielding approximately 3.4*10^38 possible addresses. This solves the IPv4 address exhaustion problem, which became critical in the early 2010s. IPv6 addresses are typically written as eight groups of four hexadecimal digits separated by colons (e.g., 2001:0db8::1). The protocol eliminates the need for Network Address Translation (NAT) in most scenarios, restoring end-to-end connectivity as originally intended for the Internet.

IPv6 integrates several features that were optional or retrofitted in IPv4. These include mandatory IPsec support (though not always enforced), simplified header format with fixed 40-byte base, and built-in multicast and anycast capabilities. Stateless address autoconfiguration (SLAAC) allows devices to generate their own global addresses without a DHCP server, using router advertisements. The neighbor discovery protocol (NDP) replaces ARP, handling address resolution and router discovery more efficiently.

IPv6 does not interoperate directly with IPv4; traffic crossing between the two stacks requires translation gateways or dual-stack implementations, where nodes run both protocols simultaneously. Adoption has been gradual: as of 2023, Google reports that roughly 40% of its users reach the search engine over IPv6. Major mobile networks and cloud providers have largely completed deployments. Enterprise and residential ISPs in many regions still operate primarily in dual-stack mode, with native IPv6 becoming more common as legacy equipment is retired.