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DHCPv6 Prefix Delegation over PPPoE
The process of DHCPv6 prefix delegation when DHCPv6 is running over a PPPoE access network is as follows:
- The CPE obtains a link-local address by appending the interface ID that it receives through IPv6CP negotiation to the IPv6 link-local prefix (FE80::/10). The link-local address provides an initial path for protocol communication between the BNG and CPE
- The CPE sends a DHCPv6 Solicit message that includes an IA_PD option.
- The BNG chooses a prefix for the CPE with information from an external AAA server or from a local prefix pool.
- The BNG sends an Advertise message to the CPE. The message includes the delegated prefix, an IA_PD option, and an IA_PD prefix option. The prefix length in the IA_PD prefix option is 48. The message can also contain other configuration information, such as a maximum lease time.
- The CPE sends a Request message to the BNG. The message requests the prefix that was advertised.
- The BNG returns the delegated prefix to the CPE in a Reply message. This message also contains the delegated prefix, an IA_PD option, and an IA_PD prefix option. The prefix length in the IA_PD prefix option is 48. The message can also contain other configuration information, such as a maximum lease time.
- The CPE uses the delegated prefix to allocate global IPv6 addresses to host devices on the subscriber network. It can use router advertisements, DHCPv6, or a combination of these two methods to allocate addresses on the subscriber LAN.
