What are the steps to configure a Cisco router as a stateless DHCPv6 (Dynamic Host Configuration Protocol version 6) server?

Enable IPv6 routing, create a DHCPv6 pool with options (DNS (Domain Name System), domain), bind it to an interface, and set the O flag.

Step-by-step:

1. Enable IPv6 routing:

R1(config)# ipv6 unicast-routing

2. Create the DHCPv6 pool:

R1(config)# ipv6 dhcp pool IPV6-STATELESS

3. Configure pool options:

R1(config-dhcpv6)# dns-server 2001:db8:acad:1::254
R1(config-dhcpv6)# domain-name example.com

4. Bind the pool to the interface and set the O flag:

R1(config)# interface g0/0/1
R1(config-if)# ipv6 dhcp server IPV6-STATELESS
R1(config-if)# ipv6 nd other-config-flag

5. Verify on clients with ipconfig /all

Key differences from DHCPv4 (Dynamic Host Configuration Protocol version 4) server config:

• No network command — the stateless server doesn't assign addresses
• No excluded addresses — SLAAC (Stateless Address Autoconfiguration) handles addressing
• The pool only contains supplementary info (DNS, domain name)
• The A flag is 1 by default, telling clients to use SLAAC for their GUA (Global Unicast Address)

Go deeper:

• RFC 8415 §5.1 — Information-request exchange — why a stateless server needs only an options pool (no address pool).