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Overview of Using DHCPv6 IA_NA with DHCPv6 Prefix Delegation

 

You can use DHCPv6 IA_NA to assign a global IPv6 address to the CPE WAN link and DHCPv6 prefix delegation to provide prefixes for use on the subscriber LAN. DHCPv6 IA_NA and DHCPv6 prefix delegation are done in a single DHCPv6 session. If the CPE sends both the IA_NA and IA_PD options in the same DHCPv6 Solicit message, the BNG returns both a single IPv6/128 address and an IPv6 prefix.

When at least one address is successfully allocated, the router creates a subscriber entry and binds the entry to the assigned address. If both addresses are successfully allocated, the router creates a single subscriber entry and binds both addresses to that entry.

Junos OS Predefined Variable for Multiple DHCPv6 Address Assignment

To configure dynamic DHCPv6 address assignment for both DHCPv6 IA_NA and DHCPv6 prefix delegation, use the $junos-subscriber-ipv6-multi-address variable In your dynamic profile. You use this variable in place of the $junos-subscriber-ipv6-address variable, which supports a single IPv6 address or prefix. The $junos-subscriber-ipv6-multi-address variable is applied as a demultiplexing source address array, and is expanded to include both the host and prefix addresses.

You include the $junos-subscriber-ipv6-multi-address variable at the [edit dynamic-profile profile-name interfaces interface-name unit logical-unit-number family inet6 demux-source] hierarchy level.

Lease Times and Session Timeouts for DHCPv6 IA_NA and DHCPv6 Prefix Delegation

When you use DHCPv6 IA_NA together with DHCPv6 prefix delegation, note the following about session timeouts and lease times:

  • A timeout from an authentication, authorization, and accounting (AAA) session has the highest precedence and overrides local pool lease times.

  • For a DHCPv6 local server, the minimum lease time associated with an address pool takes precedence over pools with longer lease times. For example, if a CPE obtains an IA_NA address from a pool with a lease time of 3600, and a prefix from a pool with a lease time of 7200, the lease time returned in the Reply message from the BNG is 3600.

  • If AAA does not return a session timeout and the address pool does not have a configured lease time, the default setting of 86,400 (one day) is used.