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Methods for Obtaining Addresses for Both DHCPv6 Prefix Delegation and DHCPv6 IA_NA

You can set up the BNG to select global IPv6 addresses to be delegated to the requesting router in one the following ways:

  • An external source such as a AAA RADIUS server or a DHCP server using the DHCPv6 relay agent.
  • Dynamic assignment from a local pool of prefixes or global IPv6 addresses that is configured on the BNG

Address assignment for prefix delegation and IA_NA are independent. For example, you can use AAA RADIUS for DHCPv6 IA_NA, and use a local pool for prefix delegation.

Address Pools for DHCPv6 Prefix Delegation and DHCPv6 IA_NA

You need two separate address pools for prefix delegation and IA_NA. The pool used for IA_NA contains /128 addresses, and the pool for prefix delegation contains /56 or /48 addresses.

You can specify the name of a delegated pool to use for prefix delegation, which means that you do not need to use AAA to obtain the pool name. In this configuration, if you have also specified a pool match order, the specified delegated pool takes precedence.

You can configure pool attributes so that the IA_NA pool and the prefix delegation pool can specify different SIP servers for DNS addresses. DHCPv6 options that the BNG returns to the CPE are based on the pool from which the addresses were allocated. These options that are returned are based on the DHCPv6 Option Request option (ORO), which can be configured globally or within the IA_NA and IA_PD request.

Using a AAA RADIUS Server to Obtain IPv6 Addresses and Prefixes

When the BNG needs to obtain a global IPv6 address for the CPE WAN link and a DHCPv6 prefix, it uses the values in one of the following RADIUS attributes:

  • Framed-IPv6-Prefix—The attribute contains a global IPv6 address and a prefix. A prefix length of 128 is associated with the global IPv6 address. Prefix lengths less than 128 are associated with prefixes.
  • Framed-IPv6-Pool—The attribute contains the name of an address-assignment pool configured on the BNG, from which the BNG can select a global IPv6 address or an IPv6 prefix to send to the CPE.

Both attributes are sent from the RADIUS server to the BNG in RADIUS Access-Accept messages.

 

Related Documentation

 

Published: 2013-07-09

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