Routing & Switching

IPv6

The 128-bit address architecture the Internet is migrating to: address types and notation, prefix planning, and the on-link machinery — Neighbor Discovery, SLAAC and DHCPv6 — that replaces ARP and re-thinks how hosts join a network.

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2 chapters

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updated 31 Aug 2026
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updated 31 Aug 2026

Contents

  1. 01IPv6 Addressing Explained: Types, Format and SubnettingIPv6 addresses are 128 bits written as eight hextets, compressible by dropping leading zeros and one run of zero hextets with ::. Global unicast addresses (2000::/3) are routable, link-local addresses (fe80::/10) exist on every interface and carry most control-plane traffic, unique local (fc00::/7) is the private range, and multicast (ff00::/8) replaces broadcast entirely; the standard LAN subnet is /64.
  2. 02Neighbor Discovery, SLAAC and DHCPv6IPv6 replaces ARP with Neighbor Discovery: ICMPv6 neighbor solicitations sent to solicited-node multicast groups resolve link-layer addresses, and router advertisements announce prefixes and gateway presence. With SLAAC a host builds its own global address from an advertised /64 prefix; RA flags decide whether DHCPv6 adds information (stateless) or assigns addresses (stateful).

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