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DHCPv6 Local Server

 

Junos OS device can act as a DHCPv6 server and allocates IP addresses to IPv6 clients. DHCPv6 server also delivers configuration settings to client hosts on a subnet or to the requesting devices that need an IPv6 prefix. The DHCPv6 local server sends and receives packets using the IPv6 protocol and informs IPv6 of the routing requirements of router clients. For more information, read this topic.

DHCPv6 Local Server Overview

The DHCPv6 local server is compatible with the DHCP local server and the DHCP relay agent, and can be enabled on the same interface as either the extended DHCP local server or DHCP relay agent.

The DHCPv6 local server provides many of the same features as the DHCP local server, including:

  • Configuration for a specific interface or for a group of interfaces

  • Site-specific usernames and passwords

  • Numbered Ethernet interfaces

  • Statically configured CoS and filters

  • AAA directed login

  • Use of the IA_NA option to assign a specific address to a client

When a DHCPv6 client logs in, the DHCPv6 local server can optionally use the AAA service framework to interact with the RADIUS server. The RADIUS server, which is configured independently of DHCP, authenticates the client and supplies the IPv6 prefix and client configuration parameters.

The client username, which uniquely identifies a subscriber or a DHCP client, must be present in the configuration in order for DHCPv6 local server to use RADIUS authentication.

You can configure DHCPv6 local server to communicate the following attributes to the AAA service framework and RADIUS at login time:

  • Client username

  • Client password

Based on the attributes that the DHCPv6 local server provides, RADIUS returns the information listed in Table 1 to configure the client:

Table 1: RADIUS Attributes and VSAs for DHCPv6 Local Server

Attribute Number

Attribute Name

Description

27

Session-Timeout

Lease time, in seconds. If not supplied, the lease does not expire

123

Delegated-IPv6-Prefix

Prefix that is delegated to the client

26-143

Max-Clients-Per-Interface

Maximum number of clients allowed per interface

To configure the extended DHCPv6 local server on the router (or switch), you include the dhcpv6 statement at the [edit system services dhcp-local-server] hierarchy level.

You can also include the dhcpv6 statement at the following hierarchy levels:

  • [edit logical-systems logical-system-name system services dhcp-local-server]

  • [edit logical-systems logical-system-name routing-instances routing-instance-name system services dhcp-local-server]

  • [edit routing-instances routing-instance-name system services dhcp-local-server]

Specifying the Delegated Address Pool for IPv6 Prefix Assignment

You can explicitly specify a delegated address pool:

  • On routers—Subscriber management uses the pool to assign IPv6 prefixes for subscribers. You can specify the delegated address pool globally, for a specific group of interfaces, or for a particular interface.

  • On switches—DHCP management uses the pool to assign IPv6 prefixes for DHCP clients. You can specify the delegated address pool globally, for a specific group of interfaces, or for a particular interface.

Note

You can also use by Juniper Networks VSA 26-161 to specify the delegated address pool. The VSA-specified value always takes precedence over the delegated-address statement.

To configure the delegated address pool for DHCPv6 local server:

  1. Specify that you want to configure override options.
  2. Configure the delegated address pool.

Preventing Binding of Clients That Do Not Support Reconfigure Messages

The DHCPv6 client and server negotiate the use of reconfigure messages. When the client can accept reconfigure messages from the server, then the client includes the Reconfigure Accept option in both solicit and request messages sent to the server.

By default, the DHCPv6 server accepts solicit messages from clients regardless of whether they support reconfiguration. You can specify that the server require clients to accept reconfigure messages. In this case, the DHCPv6 server includes the Reconfigure Accept option in both advertise and reply messages when reconfiguration is configured for the client interface. Solicit messages from nonsupporting clients are discarded and the clients are not allowed to bind.

To configure the DHCPv6 local server to bind only clients that support client-initiated reconfiguration:

  • Specify strict reconfiguration.

    For all DHCPv6 clients:

    For only a particular group of DHCPv6 clients:

The show dhcpv6 server statistics command displays a count of solicit messages that the server has discarded.

Configuring DHCPv6 Rapid Commit (MX, EX)

You can configure the DHCPv6 local server to support the DHCPv6 Rapid Commit option (DHCPv6 option 14). When rapid commit is enabled, the server recognizes the Rapid Commit option in Solicit messages sent from the DHCPv6 client. (DHCPv6 clients are configured separately to include the DHCPv6 Rapid Commit option in the Solicit messages.) The server and client then use a two-message exchange (Solicit and Reply) to configure clients, rather than the default four-message exchange (Solicit, Advertise, Request, and Reply). The two-message exchange provides faster client configuration, and is beneficial in environments in which networks are under a heavy load.

You can configure the DHCPv6 local server to support the Rapid Commit option globally, for a specific group, or for a specific interface. By default, rapid commit support is disabled on the DHCPv6 local server.

To configure the DHCPv6 local server to support the DHCPv6 Rapid Commit option:

  1. Specify that you want to configure the overrides options:
  2. Enable rapid commit support:

Verifying and Managing DHCPv6 Local Server Configuration

Purpose

View or clear information about client address bindings and statistics for the DHCPv6 local server.

Action

  • To display the address bindings in the client table on the DHCPv6 local server:

  • To display DHCPv6 local server statistics:

  • To clear all DHCPv6 local server statistics:

  • To clear all DHCPv6 local server statistics: