DHCPv6 Relay Agent Prefix Delegation Notification
DHCPv6 Relay Agent Prefix Delegation Notification allows a DHCPv6 server to dynamically delegate IPv6 prefixes to a DHCPv6 client using the DHCPv6 Prefix Delegation (PD) option. DHCPv6 prefix delegation enables an Internet Service Provider (ISP) to automate the process of assigning prefixes to a customer premises equipment (CPE) network. The CPE then assigns IPv6 subnets from the delegated IPv6 prefix to its downstream customer interfaces.
A route is added to the IPv6 route table on the provider edge router (PE) for the delegated prefix to be delegated to requesting routers. The DHCP server chooses a prefix for delegation and responds with it to the CPEx. to the external network, and to enable the correct forwarding of the IPv6 packets for the delegated IPv6 prefix. Adding the delegated prefix to the IPv6 route table ensures that the unicast Reverse Path Forwarding (uRPF) works correctly.
Because the PE is also a DHCPv6 relay agent (it relays DHCPv6 messages between the CPE and the DHCP server), it examines all DHCPv6 messages relayed between the CPE and the DHCP server and gathers information about a delegated prefix and then manages the advertisement of this delegated prefix to the external network.