386For interface-leased users, subnet-leased users, and L2VPN-leased users, the BRAS creates astatic IPoE session based on configured information after you enable IPoE on an interface. TheBRAS initiates user authentication based on the configured username and password.IPoE addressingIPoE addressing varies with user types.• DHCP users obtain IP addresses in the following sequence:{ Obtain IP addresses from the AAA-authorized IP address pool.{ Obtain IP addresses from the IP address pool configured in the ISP domain if the AAAserver does not authorize any IP address pools.{ Obtain IP addresses in the same network segment as the interface IP address if no IPaddress pool is configured in the ISP domain.• IPv6-ND-RS users obtain the AAA-authorized IPv6 prefix from IPoE, and generate an IPv6address based on the prefix. If no AAA-authorized IPv6 prefix exists, the user adopts the first64-bit IPv6 prefix of the interface to generate an IPv6 address.• Other users adopt static IP addresses or obtain IP addresses from the DHCP server withoutusing IPoE.IPoE authentication methodsIPoE supports the following authentication methods:• Bind authentication—Authenticates users by the usernames and passwords that the BRASautomatically generates based on user location information.• Web authentication—Authenticates users by the usernames and passwords that users enteron the Web authentication page.In the current software version, only the bind authentication method is supported.IPoE access procedure by using bind authenticationIPoE access by using bind authentication includes the following steps:1. The BRAS initiates authentication.The BRAS obtains information from user packets or IPoE sessions statically configured, andsends authentication requests.2. The AAA server authenticates users.The AAA server completes user authentication and sends the result to the BRAS. The securityserver, if configured, completes security authorization and sends the result to the BRAS.3. (Optional.) DHCP allocates IP addresses and IPoE allocates IPv6 prefixes.The DHCP server assigns an IP address to a DHCP user and the IPoE assigns an IPv6 prefix toan IPv6-ND-RS user.4. The BRAS performs access control.The BRAS permits the user to get online and performs access control and billing based on theauthorized result.Access procedure for DHCP usersThis section uses a DHCPv4 user as an example to illustrate the access procedure for DHCP users.The BRAS operates as a DHCP relay.
