R3303-HP HSR6800 Routers Layer 3 - IP Services Configuration Guide

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Configuring the DHCPv6 relay agent
Overview
A DHCPv6 client usually uses a multicast address to contact the DHCPv6 server on the local link to obtain
an IPv6 address and other configuration parameters. As shown in Figure 72, if the D
HCPv6 server
resides on another subnet, the DHCPv6 client can contact the server through a DHCPv6 relay agent, so
you do not need to deploy a DHCPv6 server on each subnet.
Figure 72 Typical DHCPv6 relay agent application
Figure 73 shows how the DHCPv6 client obtains an IPv6 address and other network configuration
parameters from the DHCPv6 server through the DHCPv6 relay agent, using the process of rapid
assignment involving two messages as an example.
1. The DHCPv6 client sends a Solicit message containing the Rapid Commit option to the multicast
address FF02::1:2 of all DHCPv6 servers and relay agents.
2. After receiving the Solicit message, the DHCPv6 relay agent encapsulates the message into the
Relay Message option of a Relay-forward message, and sends the message to the DHCPv6 server.
3. After obtaining the Solicit message from the Relay-forward message, the DHCPv6 server selects an
IPv6 address and other required parameters, and adds them to the reply which is encapsulated
within the Relay Message option of a Relay-reply message. The DHCPv6 server then sends the
Relay-reply message to the DHCPv6 relay agent.
4. The DHCPv6 relay agent obtains the reply from the Relay-reply message and sends the reply to the
DHCPv6 client.
Then the DHCPv6 client uses the IPv6 address and other network parameters assigned by the DHCPv6
server to perform network configuration.