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    Limiting the Maximum Number of IPv6 Prefixes Delegated Per Interface by the DHCPv6 Local Server Overview

    You can limit the maximum number of IP version 6 (IPv6) prefixes offered per interface by the Dynamic Host Configuration Protocol version 6 (DHCPv6) local server to DHCPv6 subscribers. The limit value for the offered IPv6 prefixes can be set as a global limit for all interfaces of a particular interface type or as an individual limit for a specific interface or subinterface. You can use the ipv6 dhcpv6-local limit command to set the limit for the number of IPv6 prefixes offered by the DHCPv6 local server. With the ipv6 dhcpv6-local limit command, you can set the global limit for the following interface types:

    • Asynchronous Transfer Mode (ATM)
    • Ethernet
    • Virtual LAN (VLAN)
    • Packet over SONET

      Note: The DHCPv6 local server is not supported over the packet over SONET (POS) access interface.

    When you set the limit value as a global limit for an interface type, all dynamically or statically created interfaces of that type inherit the global limit value. By default, the limit value is set as 48,000 for ATM, Ethernet, and VLAN interface types.

    You can override the inherited global limit value for a particular interface by configuring an individual limit for that interface. You can use the interface keyword with the ipv6 dhcpv6-local limit command to configure the individual limit.

    The global limits for interface types and the individual limits set on static interfaces are stored in nonvolatile storage (NVS). These values are restored during a switchover or a reload.

    When you assign an individual limit to a dynamic interface, that limit is in force only until either a switchover or reload takes place. After the switchover or reload, if the action that caused the dynamic interface to be created occurs again, a new dynamic interface is created. The new dynamic interface then inherits the limit set by the global values based on the type of interface that is created.

    Note: Limits that you specify on dynamic interfaces are not restored after a switchover or reboot.

    A subinterface table is maintained for both DHCPv6 standalone and authenticate modes to validate the IPv6 prefix limit per interface when the subscriber tries to connect with the local server. The table contains the following information:

    • Number of subscribers connected
    • Number of subscribers denied upon exceeding the configured prefix limit
    • Total number of subscribers attempted
    • Type of the subinterface


    • When you upgrade the JunosE Software by using the unified ISSU from the old release not containing this feature to the new release containing this feature, the subscriber count is retrieved and added to the subinterface table.
    • The IPv6 prefix limit per interface is supported only for the existing Identity Association Prefix Delegation option.

    Published: 2014-08-13