SLAAC vs DHCPv6

SLAAC Stateless DHCPv6 Stateful DHCPv6 Address from client itself client (RA prefix) server DNS no yes yes RA flags M=0 O=0 M=0 O=1 M=1 SLAAC: Router Solicitation → Router Advertisement (prefix + gateway as the router’s link-local) → client builds its Interface ID (EUI-64 or privacy random) → DAD. No server, no logs, and only […]

IPv6 Address Formats — Cheat Sheet

Address formats at a glance Type Prefix Scope Use Global Unicast 2000::/3 Global The routable address Link-Local FE80::/10 Link ND + routing protocols, auto-generated Unique Local FC00::/7 (FD00::/8) Private Internal, never internet-routed Multicast FF00::/8 Varies One-to-many, replaces broadcast Anycast no fixed prefix Varies Same address on many devices, nearest wins Loopback ::1/128 Local Stack test […]

What is IPv6?

IPv6 replaces IPv4: 128-bit addresses, hexadecimal notation, no NAT requirement, no broadcast (multicast instead). 2001:0db8:abcd:0012:0000:0000:0000:0001 = 2001:db8:abcd:12::1 Structure Network prefix + Interface ID; /64 is the standard subnet — first 64 bits network, last 64 host. SLAAC only works on /64 (classic trap). Address types Global Unicast — 2000::/3, the internet-routable one Link-Local — FE80::/10, […]

The IPv6 Header

A fixed 40-byte Layer 3 header (RFC 8200) designed for fast hardware forwarding — no checksum, no options inside the base header, extensions as modular headers. Fields Field Size Purpose Version 4 bits Always 6 Traffic Class 8 bits QoS (DSCP + ECN) Flow Label 20 bits Flow identity for QoS/load-balancing Payload Length 16 bits […]