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DHCPv6 Relay Agent

The DHCPv6 relay agent enhances the DHCP relay agent by providing support in an IPv6 network. The DHCPv6 relay agent passes messages between the DHCPv6 client and the DHCPv6 server, similar to the way DHCP relay agent supports an IPv4 network. DHCPv6 relay agents eliminate the necessity of having a DHCPv6 server on each physical network. For more information about inserting DHCPv6 Interface-ID (Option 18), Remote-ID (Option 37) or Client MAC Address (Option 79) in DHCPv6 packets, and verifying the DHCPv6 configuration, read this topic.

DHCPv6 Relay Agent Overview

When a DHCPv6 client logs in, the DHCPv6 relay agent uses the AAA service framework to interact with the RADIUS server to provide authentication and accounting. The RADIUS server, which is configured independently of DHCP, authenticates the client and supplies the IPv6 prefix and client configuration parameters, such as session timeout and the maximum number of clients allowed per interface.

Note:

The PTX Series Packet Transport Routers do not support authentication for DHCPv6 relay agents.

Note:

The following DHCPv6 functionalities are not supported on ACX Series routers:

  • Subscriber authentication for DHCPv6 relay agents

  • DHCP snooping

  • DHCPv6 client

  • Liveness detection

  • Dynamic profiles

  • Option 37 support for remote ID insertion

  • Bidirectional Forwarding Detection (BFD) for DHCPv6 relay

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

To configure the DHCPv6 relay agent on the router (or switch), you include the dhcpv6 statement at the [edit forwarding-options dhcp-relay] hierarchy level.

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

  • [edit logical-systems logical-system-name forwarding-options dhcp-relay]

  • [edit logical-systems logical-system-name routing-instances routing-instance-name forwarding-options dhcp-relay]

  • [edit routing-instances routing-instance-name forwarding-options dhcp-relay]

See DHCPv6 Monitoring and Management for commands specific to viewing and clearing DHCPv6 bindings and statistics.

Inserting DHCPv6 Interface-ID Option (Option 18) In DHCPv6 Packets

You can configure DHCPv6 relay agent to insert the DHCPv6 Interface-ID (option 18) in the packets that the relay sends to a DHCPv6 server. You can configure the option 18 support at either the DHCPv6 global or group level.

When you configure option 18 support, you can optionally include the following additional information:

  • Prefix—Specify the prefix option to add a prefix to the interface identifier. The prefix can be any combination of hostname, logical system name, and routing instance name.

  • Interface description—Specify the use-interface-description option to include the textual interface description instead of the interface identifier. You can include either the device interface description or the logical interface description.

  • Option 82 Agent Circuit ID suboption (suboption 1)—Specify the use-option-82 option to include the DHCPv4 Option 82 Agent Circuit ID suboption (suboption 1). This configuration is useful in a dual-stack environment, which has both DHCPv4 and DHCPv6 subscribers that reside over the same underlying logical interface. The router checks for the option 82 suboption 1 value and inserts it into the outgoing packets. If no DHCPv4 binding exists or if the binding does not have an option 82 suboption 1 value, the router sends the packets without adding an option 18.

Note:

If you specify one of the optional configurations, and the specified information does not exist (for example, there is no interface description), DHCPv6 relay ignores the optional configuration and inserts the default interface identifier in the packets.

To insert the DHCPv6 Interface-ID option (option 18) in DHCPv6 packets:

  1. Configure the DHCPv6 relay to include option 18.
  2. (Optional) Specify the prefix to include in option 18.
  3. (Optional) Specify that option 18 include the textual description of the interface. You can specify either the logical interface description or the device interface description.
  4. (Optional) Specify that option 18 use the DHCPv4 Option 82 Agent Circuit ID suboption (suboption 1) value.

Inserting DHCPv6 Remote-ID Option (Option 37) In DHCPv6 Packets

Starting in Junos OS Release 14.1, you can configure DHCPv6 relay agent to insert DHCPv6 Remote-ID (option 37) in the packets that the relay sends to a DHCPv6 server. You can configure option 37 support at either the DHCPv6 global or group level.

When you configure option 37 support, you can optionally include the following information:

  • Prefix—Specify the prefix option to add a prefix to the interface identifier. The prefix can be any combination of hostname, logical system name, and routing instance name.

  • Interface description—Specify the use-interface-description option to include the textual interface description instead of the interface identifier. You can include either the device interface description or the logical interface description.

  • Option 82 Agent Remote-ID suboption (suboption 2)—Specify the use-option-82 option to use the value of the DHCPv4 option 82 Remote-ID suboption (suboption 2). This configuration is useful in a dual-stack environment, which has both DHCPv4 and DHCPv6 subscribers that reside over the same underlying logical interface. The router checks for the option 82 suboption 2 value and inserts it into the outgoing packets.

Note:

If you specify one of the optional configurations, and the specified information does not exist (for example, there is no interface description), DHCPv6 relay ignores the optional configuration and inserts the default interface identifier in the packets.

To insert the DHCPv6 Remote-ID option (option 37) in DHCPv6 packets:

  1. Configure the DHCPv6 relay to include option 37.
  2. (Optional) Specify the prefix to include with the option 37 information.
  3. (Optional) Specify that option 37 include the textual description of the interface. You can specify either the logical interface description or the device interface description.
  4. (Optional) Specify that option 37 use the DHCPv4 option 82 Remote-ID suboption (suboption 2) value.

    If no DHCPv4 binding exists, or if the binding does not include an option 82 suboption 2 value, by default the router sends the packets without adding option 37. However, you can use the optional strict keyword to specify that the router drop packets that do not have a suboption 2 value.

Inserting the DHCPv6 Client MAC Address Option (Option 79) In DHCPv6 Packets

The incremental deployment of IPv6 to existing IPv4 networks can result in a dual-stack network environment in which devices act as both DHCPv4 and DHCPv6 clients. In dual-stack scenarios, operators need to be able to associate DHCPv4 and DHCPv6 messages with the same client interface, based on an identifier that is common to the interface.

You can configure a DHCPv6 relay agent to insert the DHCPv6 client MAC address in the packets that the relay sends to a DHCPv6 server. The client MAC address is used to associate DHCPv4 and DHCPv6 messages with the same client interface.

In addition to associating DHCPv4 and DHCPv6 messages from a dual-stack client, having the client MAC address in DHCPv6 packets provides additional information for event debugging and logging related to the client at the relay agent and the server.

When DHCPv6 option 79 is enabled, the DHCPv6 relay agent reads the source MAC address of DHCPv6 Solicit and DHCPv6 Request messages that it receives from a client. The relay agent encapsulates the Solicit and Request messages within a DHCPv6 Relay-Forward message, and inserts the client MAC address as option 79 in the Relay-Forward header before relaying the message to the server.

If the DHCPv6 packet already has a Relay-Forward header, the DHCPv6 relay agent adds the client MAC address if the packet meets the following conditions: the packet has only one Relay-Forward header, the Relay-Forward header was added by an LDRA, and the Relay-Forward header does not already include option 79 information.

You can also configure DHCPv6 option 79 for a lightweight DHCPv6 relay agent (LDRA). An LDRA resides on the same IPv6 link as the DHCPv6 client and relay agent or server and acts as a layer 2 relay agent, without performing the routing function necessary to forward messages to a server or relay agent that resides on a different IPv6 link.

To configure DHCPv6 option 79 for a DHCPv6 relay agent (layer 3):
  • To configure DHCPv6 option 79 for an LDRA (layer 2):

Verifying and Managing DHCPv6 Relay Configuration

Purpose

View or clear address bindings or statistics for extended DHCPv6 relay agent clients:

Action

  • To display the address bindings for extended DHCPv6 relay agent clients:

  • To display extended DHCPv6 relay agent statistics:

  • To clear the binding state of DHCPv6 relay agent clients:

  • To clear all extended DHCPv6 relay agent statistics:

Release History Table
Release
Description
14.1
Starting in Junos OS Release 14.1, you can configure DHCPv6 relay agent to insert DHCPv6 Remote-ID (option 37) in the packets that the relay sends to a DHCPv6 server.