3.1.b (ix) DHCPv6 prefix delegation
IPv6 prefix delegation is a way for upstream routers to assign subnets to downstream DHCP servers/routers.
This has more of a use case in the ISP world where the ISP wants to assign specific public blocks to clients.
Here is the configuration:
ISP-R1:
en conf t ipv6 unicast-routing ipv6 local pool DHCPPOOLDELEGATION 2000:1111:9900::/40 48 ipv6 dhcp pool DHCPPOOL prefix-delegation pool DHCPPOOLDELEGATION lifetime 1800 600 link-address 2000:9999::1/64 dns-server 2000:9999::1 domain-name mytest.com ipv6 dhcp server DHCPPOOL exit int g0/0 ipv6 enable ipv6 address 2000:9999:1/64 ipv6 dhcpserver DHCPPOOL no shut
ISP-R2:
en conf t ipv6 unicast-routing int g0/0 ipv6 enable ipv6 address autoconfig default ipv6 dhcp client pd prefix-from-provider no shut exit int g0/1 ipv6 enable ipv6 address prefix-from-provider ::1:1/64 no shut
CLIENT:
en conf t ipv6 unicast-routing int g0/1 ipv6 enable ipv6 address autoconfig default
Source:
https://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113141-DHCPv6-00.html