What is Stateful DHCPv6 and how does it differ from SLAAC?

Stateful DHCPv6 works like classic IPv4 DHCP — the DHCPv6 server hands out and tracks the actual IPv6 addresses; SLAAC is not used at all.

This is the "do it the IPv4 way" option:

• The client requests its address from the DHCPv6 server, which assigns it and keeps state (a lease, mapping address ↔ client)
• No SLAAC — the router doesn't supply the address
• Additional info (NTP, DNS) is delivered in the same exchange
• Communication uses UDP port 546 (client) and UDP port 547 (server) — note these differ from DHCPv4's ports 67/68

Tip: Choose stateful DHCPv6 when an organisation wants central control and an audit trail of exactly which host has which address — something pure SLAAC can't give you.

Go deeper:

• DHCPv6 — Stateful Address Configuration (Elektronik-Kompendium, DE) — the full client/server exchange and why DHCPv6 still rides alongside Router Advertisements.