Overview of IPv6 Address Management

Configuring a static IPv6 address

A user can configure a static IPv6 address. After the user goes offline, the static IPv6 address cannot be assigned to other users.

Receiving an IPv6 address from the RADIUS server

The NetEngine 8000 F allows the RADIUS server to use NDRA or DHCPv6 (IA_PD) to allocate IPv6 prefixes and use DHCPv6 (IA_NA) to allocate IPv6 addresses to users. If an address allocated to a user by the RADIUS server is part of the local address pool, the prefix length allocated by the RADIUS server must be consistent with that of the local address pool. If prefix lengths are different, route forwarding for this user will be affected.

Dynamically obtaining an IPv6 address through dynamic allocation protocols

IPv4 has two address dynamic allocation protocols: IPCP and DHCPv4. IPv6 has two global unicast address allocation protocols: ND and DHCPv6. IPv6CP is used to negotiate link-local addresses.

• Stateless address allocation using ND

  Stateless address allocation is implemented using ND. ND replaces the Address Resolution Protocol (ARP) and ICMP Router Discovery on an IPv4 network. ND also provides functions such as neighbor unreachability detection (NUD), duplicate address detection (DAD), and address autoconfiguration.

  IPv6 stateless address allocation is implemented through interaction between router solicitation (RS) and router advertisement (RA) packets.

  1. The client sends an RS packet.
  2. After receiving the RS packet, the NetEngine 8000 F replies an RA packet, including the following information.
     • Whether address autoconfiguration is enabled
     • M flag and O flag information
     • One or multiple link prefixes (nodes on the local link can automatically generate addresses using these address prefixes) and the lifetime of link prefixes
     • Whether the router that sends the RA packet can function as a default router (if the router can function as a default router, the lifetime of the default router is also contained in the message, expressed in seconds.)
     • Other configuration information about the client, such as the hop limit and the MTU of packets initiated by the client
  3. The client receives an RA packet from the router. If address autoconfiguration is specified in the RA packet, the M flag is 0, and the RA packet contains correct link prefixes, the client uses the link prefixes and interface IDs to generate global unicast addresses.

  The IP address lease is renewed when the NetEngine 8000 F sends an RA packet with a new lifetime.

  Advantages:

  • The stateless address allocation is simple, and all IPv6 nodes support ND.

  • Addresses are automatically allocated without any servers. The clients do not have to support DHCPv6 clients.

• Stateful address allocation using DHCPv6

  In the interaction between RS and RA packets, if the M flag is 0 and the O flag is 1, the clients need to obtain other configuration information except IPv6 addresses in stateful mode; if the M flag is 1 in the RA packet, the clients need to obtain IPv6 addresses and other configuration information in stateful mode.

  Stateful information configuration and stateful address configuration all use DHCPv6. The client requests configuration from the server, and the server replies with corresponding configuration according to policies.

  • Identity associations for non-temporary addresses (IA_NA): allocating IPv6 addresses using the IA_NA option in DHCP messages

  • Identity associations for prefix delegation (IA_PD): allocating IPv6 prefixes using the IA_PD option in DHCP messages

  Advantages:

  • Flexible configuration functions: DHCPv6 offers more information to the clients and allocates parameters such as the desired addresses.
  • Better manageability: DHCPv6 can offer detailed management information.
  • Expansibility: Some options of DHCPv6 packets can be defined by vendors, increasing the expandability.