How do you configure a Cisco router as a stateful DHCPv6 (Dynamic Host Configuration Protocol version 6) client?

Enable IPv6 routing, create a link-local address with ipv6 enable, then use ipv6 address dhcp to request all configuration from a stateful DHCPv6 server.

Step-by-step:

1. Enable IPv6 routing:

R2(config)# ipv6 unicast-routing

2. Create a link-local address:

R2(config)# interface g0/0/1
R2(config-if)# ipv6 enable

3. Request address from DHCPv6:

R2(config-if)# ipv6 address dhcp

4. Verify the GUA (Global Unicast Address):

R2# show ipv6 interface brief

5. Verify DHCPv6 info received:

R2# show ipv6 dhcp interface g0/0/1

Key difference from stateless client:

• Stateless: ipv6 address autoconfig — creates own GUA via SLAAC (Stateless Address Autoconfiguration)
• Stateful: ipv6 address dhcp — receives GUA from DHCPv6 server

Tip: The command mirrors DHCPv4 (Dynamic Host Configuration Protocol version 4) client config (ip address dhcp). Both autoconfig and dhcp require ipv6 enable first to have a LLA (Link-Local Address) for communication.

Go deeper:

• DHCPv6 (Wikipedia) — the client SOLICIT/REQUEST ipv6 address dhcp triggers to obtain a server-assigned GUA.