2. If the DHCPv6 server supports rapid assignment, it responds with a Reply message containing the assigned IPv6 address/prefix and other configuration parameters. If the DHCPv6 server does not support rapid assignment, Assignment involving four messages is performed.

Figure 1 Rapid assignment involving two messages

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Assignment involving four messages

As shown in Figure 2, four-message assignment operates using the following steps:

1. The DHCPv6 client sends a Solicit message to request an IPv6 address/prefix and other configuration parameters.

2. The DHCPv6 server responds with an Advertise message that contains the assignable address/prefix and other configuration parameters if either of the following conditions exists:

¡ The Solicit message does not contain a Rapid Commit option.

¡ The DHCPv6 server does not support rapid assignment even though the Solicit message contains a Rapid Commit option.

3. The DHCPv6 client might receive multiple Advertise messages offered by different DHCPv6 servers. It selects an offer according to the receiving sequence and server priority, and sends a Request message to the selected server for confirmation.

4. The DHCPv6 server sends a Reply message to the client, confirming that the address/prefix and other configuration parameters are assigned to the client.

Figure 2 Assignment involving four messages

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Address/prefix lease renewal

An IPv6 address/prefix assigned by a DHCPv6 server has a valid lifetime. After the valid lifetime expires, the DHCPv6 client cannot use the IPv6 address/prefix. To use the IPv6 address/prefix, the DHCPv6 client must renew the lease time.

Figure 3 Using the Renew message for address/prefix lease renewal

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As shown in Figure 3, at T1, the DHCPv6 client sends a Renew message to the DHCPv6 server. The recommended value for T1 is half the preferred lifetime. The DHCPv6 server responds with a Reply message, informing the client whether the lease is renewed.

Figure 4 Using the Rebind message for address/prefix lease renewal

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As shown in Figure 4:

· If the DHCPv6 client does not receive a response from the DHCPv6 server after sending a Renew message at T1, it multicasts a Rebind message to all DHCPv6 servers at T2. Typically, the value for T2 is 0.8 times the preferred lifetime.

· The DHCPv6 server responds with a Reply message, informing the client whether the lease is renewed.

· If the DHCPv6 client does not receive a response from any DHCPv6 server before the valid lifetime expires, the client stops using the address/prefix.

For more information about the valid lifetime and the preferred lifetime, see "Configuring basic IPv6 settings."

Stateless DHCPv6

Stateless DHCPv6 enables a device that has obtained an IPv6 address/prefix to get other configuration parameters from a DHCPv6 server.

The device performs stateless DHCPv6 if an RA message with the following flags is received from the router during stateless address autoconfiguration:

· The managed address configuration flag (M flag) is set to 0.

· The other stateful configuration flag (O flag) is set to 1.

Figure 5 Stateless DHCPv6 operation

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As shown in Figure 5, stateless DHCPv6 operates in the following steps:

1. The DHCPv6 client sends an Information-request message to the multicast address of all DHCPv6 servers and DHCPv6 relay agents. The Information-request message contains an Option Request option that specifies the requested configuration parameters.

2. The DHCPv6 server returns to the client a Reply message containing the requested configuration parameters.

3. The client checks the Reply message. If the obtained configuration parameters match those requested in the Information-request message, the client uses these parameters to complete configuration. If not, the client ignores the configuration parameters. If the client receives multiple replies with configuration parameters matching those requested in the Information-request message, it uses the first received reply.

DHCPv6 options

Option 18

Option 18, also called the interface-ID option, is used by the DHCPv6 relay agent to determine the interface to use to forward RELAY-REPLY message.

The DHCPv6 snooping device adds Option 18 to the received DHCPv6 request message before forwarding it to the DHCPv6 server. The server then assigns IP address to the client based on the client information in Option 18.

Figure 6 Option 18 format

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Figure 6 shows the Option 18 format, which includes the following fields:

· Option code—Option code. The value is 18.

· Option length—Size of the option data.

· Port index—Port that receives the DHCPv6 request from the client.

· VLAN ID—ID of the outer VLAN.

· Second VLAN ID—ID of the inner VLAN. This field is optional. If the received DHCPv6 request does not contain a second VLAN, Option 18 also does not contain it.

· DUID—DUID of the DHCPv6 client.

Option 37

Option 37, also called the remote-ID option, is used to identify the client.

The DHCPv6 snooping device adds Option 37 to the received DHCPv6 request message before forwarding it to the DHCPv6 server. This option provides client information about address allocation.

Figure 7 Option 37 format

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Figure 7 shows the Option 37 format, which includes the following fields:

· Option code—Option code. The value is 37.

· Option length—Size of the option data.

· Enterprise number—Enterprise number.

· Port index—Port that receives the DHCPv6 request from the client.

· VLAN ID—ID of the outer VLAN.

· Second VLAN ID—ID of the inner VLAN. This field is optional. If the received DHCPv6 request does not contain a second VLAN, Option 37 also does not contain it.

· DUID—DUID of the DHCPv6 client.

Protocols and standards

· RFC 3736, Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6

· RFC 3315, Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

· RFC 2462, IPv6 Stateless Address Autoconfiguration

· RFC 3633, IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6

Configuring the DHCPv6 relay agent

About DHCPv6 relay agent

Typical application

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 8, if the DHCPv6 server resides on another subnet, the DHCPv6 clients need a DHCPv6 relay agent to contact the server. The relay agent feature avoids deploying a DHCPv6 server on each subnet.

Figure 8 Typical DHCPv6 relay agent application

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DHCPv6 relay agent operating process

As shown in Figure 9, a DHCPv6 client obtains an IPv6 address and other network configuration parameters from a DHCPv6 server through a DHCPv6 relay agent. The following example uses rapid assignment to describe the process:

· The DHCPv6 client sends a Solicit message containing the Rapid Commit option to the multicast address FF02::1:2 of all the DHCPv6 servers and relay agents.

· 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.

· After obtaining the Solicit message from the Relay-forward message, the DHCPv6 server performs the following tasks:

¡ Selects an IPv6 address and other required parameters.

¡ Adds them to a reply that is encapsulated within the Relay Message option of a Relay-reply message.

¡ Sends the Relay-reply message to the DHCPv6 relay agent.

· The DHCPv6 relay agent obtains the reply from the Relay-reply message and sends the reply to the DHCPv6 client.

· The DHCPv6 client uses the IPv6 address and other network parameters assigned by the DHCPv6 server to complete network configuration.

Figure 9 Operating process of a DHCPv6 relay agent

Restrictions and guidelines: DHCPv6 relay configuration

For traffic from the DHCPv6 clients attached to a relay interface to be forwarded correctly, the subnet used for assigning IPv6 addresses to them must be the subnet in which the relay interface is located.

DHCPv6 relay agent tasks at a glance

To configure a DHCPv6 relay agent, perform the following tasks:

1. Enabling the DHCPv6 relay agent on an interface

2. Specifying DHCPv6 servers on the relay agent

3. (Optional.) Specifying a gateway address for DHCPv6 clients

4. (Optional.) Specifying the source IPv6 address for relayed DHCPv6 requests

5. (Optional.) Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 relay agent

6. (Optional.) Specifying a padding mode for the Interface-ID option

7. (Optional.) Enabling the DHCPv6 relay agent to support Option 79

8. (Optional.) Enabling the DHCPv6 relay agent to advertise IPv6 prefixes

9. (Optional.) Configuring DHCPv6 relay security features

Enabling the DHCPv6 relay agent on an interface

Restrictions and guidelines

As a best practice, do not enable DHCPv6 relay agent and DHCPv6 client on the same interface.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Enable DHCPv6 relay agent on the interface.

ipv6 dhcp select relay

By default, the DHCPv6 relay agent is disabled on the interface.

Specifying DHCPv6 servers on the relay agent

Specifying DHCPv6 server IP addresses

Restrictions and guidelines

· You can use the ipv6 dhcp relay server-address command to specify a maximum of eight DHCPv6 servers on the DHCPv6 relay agent interface. The DHCPv6 relay agent forwards DHCP requests to all the specified DHCPv6 servers.

· If a DHCPv6 server address is a link-local address or multicast address, you must specify an outgoing interface by using the interface keyword in this command. Otherwise, DHCPv6 packets might fail to reach the DHCPv6 server.

· The DHCPv6 relay agent forwards the packets from clients to the specified DHCPv6 server in the specified virtual network (MPLS L3VPN instance or the public network). If you do not specify an MPLS L3VPN instance or the public network, the DHCPv6 relay agent forwards the packets from a client in the same virtual network as the client.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Specify a DHCPv6 server.

ipv6 dhcp relay server-address ipv6-address [ interface interface-type interface-number | public | vpn-instance vpn-instance-name ]

By default, no DHCPv6 server is specified.

Specifying DHCPv6 servers for a DHCPv6 relay address pool

About this task

This feature allows DHCPv6 clients of the same type to obtain IPv6 addresses, IPv6 prefixes, and other configuration parameters from the DHCPv6 servers in the matching DHCPv6 relay address pool.

It applies to scenarios where the DHCPv6 relay agent connects to clients of the same access type but classified into different types by their locations. In this case, the relay interface typically has no IPv6 address configured. You can use the gateway-list command to specify the gateway addresses for clients matching the same DHCPv6 relay address pool.

Upon receiving a DHCPv6 Solicit or Request from a client that matches a DHCPv6 relay address pool, the relay agent processes the packet as follows:

· Fills the link-address field of the packet with a specified gateway address.

· Forwards the packet to all DHCPv6 servers in the matching DHCPv6 relay address pool.

The DHCPv6 servers select an IPv6 address pool according to the gateway address.

Restrictions and guidelines

· You can specify a maximum of eight DHCPv6 servers for one DHCPv6 relay address pool for high availability. The relay agent forwards DHCPv6 Solicit and Request packets to all DHCPv6 servers in the DHCPv6 relay address pool.

Procedure

1. Enter system view.

system-view

2. Create a DHCPv6 relay address pool and enter its view.

ipv6 pool pool-name

3. Specify gateway addresses for the clients matching the DHCPv6 relay address pool.

gateway-list ipv6-address&<1-8>

By default, no gateway address is specified.

4. Specify DHCPv6 servers for the DHCPv6 relay address pool.

remote-server ipv6-address [ interface interface-type interface-number | public | vpn-instance vpn-instance-name ]

By default, no DHCPv6 server is specified for the DHCPv6 relay address pool.

Specifying the DHCPv6 server selection algorithm

About this task

The DHCPv6 relay agent supports the polling and master-backup DHCPv6 server selection algorithms.

By default, the DHCPv6 relay agent uses the polling algorithm. It forwards DHCPv6 requests to all DHCPv6 servers. The DHCPv6 clients select the DHCPv6 server from which the first received DHCP reply comes.

If the DHCPv6 relay agent uses the master-backup algorithm, it forwards DHCPv6 requests to the master DHCPv6 server first. If the master DHCPv6 server is not available, the relay agent forwards the subsequent DHCPv6 requests to a backup DHCPv6 server. If the backup DHCPv6 server is not available, the relay agent selects the next backup DHCP server, and so on. If no backup DHCPv6 server is available, it repeats the process starting from the master DHCPv6 server.

In a network where remote BAS IP pools are configured on the DHCPv6 relay agent, the first specified DHCPv6 server in the pool is the master. The other DHCP servers in the pool are backup.

Procedure

1. Enter system view.

system-view

2. Enter IPv6 address pool view.

ipv6 pool pool-name

3. Specify the DHCPv6 server selection algorithm.

remote-server algorithm { master-backup | polling }

By default, the polling algorithm is used. The DHCPv6 relay agent forwards DHCPv6 requests to all DHCPv6 servers.

Configuring DHCPv6 server liveness detection

About this task

This feature is applicable when the relay agent selects a DHCPv6 server from a DHCPv6 address pool.

This feature enables the relay agent to detect the liveness of the DHCPv6 servers.

The DHCPv6 server liveness detection mechanism differs depending on the server selection algorithm.

If the master-backup selection algorithm applies, the relay agent uses the following mechanism to determine whether a DHCPv6 server is available:

1. When relaying the first request to a selected DHCPv6 server, the DHCPv6 relay agent starts the request counter and the timeout timer configured for that server.

2. The relay agent determines the availability of the DHCPv6 server:

¡ On receipt of a reply before the timeout timer expires, the relay agent resets the request counter and stops the timeout timer.

The agent determines that the DHCPv6 server is not available and places it in down state, if the reply indicates an address or prefix assignment failure.

The relay agent restarts the timer and the request counter when it relays a new request to the server.

¡ If the relay agent has not received a reply from the server when the timeout timer expires, the relay agent checks the request counter against the dead-count-value setting.

- If the number of requests does not exceed the dead-count-value setting, the relay agent continues to send new requests to the server without resetting the request counter.

- If the number of requests exceeds the dead-count-value setting, the relay agent determines that the DHCPv6 server is not available and places it in down state.

3. On receipt of a new request after it placed the server in down state, the relay agent forwards the new request to the next available server.

4. If none of the servers are available, the relay agent forwards the new request to all servers. In this situation, the relay agent does not start the timeout timer.

If the polling selection algorithm applies, the relay agent uses the following mechanism to determine whether a DHCPv6 server is available:

1. When receiving the first request, the DHCPv6 relay agent forwards that request to all available servers. At the same time, it starts the request counter and the timeout timer. The timeout timer is set to the highest timeout value among all servers.

2. The relay agent determines the availability of the DHCPv6 server:

¡ On receipt of a reply before the timeout timer expires, the relay agent takes one of the following actions depending on the reply content:

- If the reply contains a usable IPv6 address or prefix, the relay agent resets the request counter and stops the timeout timer.

- If the reply indicates an address or prefix assignment failure, the relay agent determines that the reply sender is unavailable and places it in down state. In this situation, the relay agent does not reset the request counter. It continues to wait for replies from other servers until a reply is received or until the timeout timer expires.

¡ If the relay agent has not received a reply from any servers when the timeout timer expires, the relay agent checks the request counter again the dead-count-value setting.

- If the number of requests does not exceed the dead-count-value setting, the relay agent continues to send new requests to all servers without resetting the request counter.

- If the number of requests exceeds the dead-count-value setting, the relay agent determines that none of the DHCPv6 servers is available and places them in down state.

3. When the relay agent receives a new request after it placed all the servers in down state, it forwards the new request to all the servers without restarting the timeout timer.

The relay agent starts the dead-time timer for a DHCPv6 server after it determines that the server is unavailable. The relay agent will not relay requests to that server until after the timer expires.

When a DHCPv6 server is marked as dead, the relay agent starts the dead time for the server. Within the dead period, the relay agent does not relay any packets to this DHCPv6 server. After the dead period expires, the relay agent determines that the DHCPv6 server becomes alive, and starts forwarding packets to this server.

Restrictions and guidelines

The liveness detection settings specific to a DHCP server have a higher priority than the shared settings. If no DHCP server-specific settings are configured, the shared ones apply.

You can specify multiple server liveness detection rules for different DHCPv6 server addresses. If you do not specify a DHCPv6 server for the command, you are creating a shared detection rule. The DHCP server-specific detection rule or the shared rule takes effect as follows:

· If you specify the same rule keyword but with different values in each command execution, the most recent configuration takes effect.

· If you specify different rule keywords in each command execution, all configurations take effect.

Procedure

1. Enter system view.

system-view

2. Configure DHCPv6 server liveness detection.

ipv6 dhcp remote-server [ ipv6-address [ vpn-instance vpn-instance-name ] ] { dead-count dead-count-value | dead-time dead-time | timeout timeout } *

By default, the relay agent marks the DHCP server as dead if the DHCP relay agent does not receive a reply from a DHCP server within 55 seconds.

Specifying a gateway address for DHCPv6 clients

About this task

By default, the DHCPv6 relay agent fills the link-address field of DHCPv6 Solicit and Request packets with the first IPv6 address of the relay interface. This task is required if a relay interface connects to multiple subnets and you want the DHCP server to assign IPv6 addresses to clients in a specific subnet. When receiving DHCPv6 Solicit and Request packets from a client of this subnet, the DHCPv6 relay agent uses the specified gateway address to fill the link-address field of the packets.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Specify a gateway address for DHCPv6 clients.

ipv6 dhcp relay gateway ipv6-address

By default, the DHCPv6 relay agent uses the first IPv6 address of the relay interface as the clients' gateway address.

Specifying the source IPv6 address for relayed DHCPv6 requests

About specifying the source IP address for relayed DHCP requests

This task is required if multiple relay interfaces share the same IPv6 address or if a relay interface does not have routes to DHCPv6 servers. You can use this command to specify the IPv6 address of another interface (typically a loopback interface) on the DHCPv6 relay agent as the source IPv6 address for relayed DHCP requests.

Restrictions and guidelines

Specify the gateway keyword if the DHCPv6 relay agent has a reachable route to the DHCPv6 address from the address filled in the Link-address field.

Specifying the source IP address for relayed DHCP requests (DHCPv6 relay address pool view)

1. Enter system view.

system-view

2. Enter DHCPv6 relay address pool view.

ipv6 pool pool-name

3. Specify the source IPv6 address of the DHCPv6 requests that the DHCPv6 relay agent forwards to the DHCPv6 server.

dhcpv6-relay source-address { ipv6-address | gateway | interface interface-type interface-number }

By default, the source IPv6 address for replayed DHCPv6 requests is the IPv6 address of the output interface through which the DHCPv6 relay agent reaches the DHCPv6 server.

Specifying the source IP address for relayed DHCP requests (interface view)

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Specify the source IP address for DHCP requests.

ipv6 dhcp relay source-address { ipv6-address | interface interface-type interface-number }

The relay agent chooses the default source IPv6 address for relayed requests depending on whether its server-side interface and the DHCPv6 server belong to the same VPN instance:

¡ If they belong to the same VPN instance, the relay agent uses one of the global unicast addresses on the output interface for relayed requests.

¡ If they belong to different VPN instances, the relay agent uses the lowest IPv6 address that is in the same VPN instance as the DHCPv6 server.

If the specified interface does not have a global unicast IPv6 address, the relay agent follows the default rule to specify the source address for relayed DHCPv6 requests.

Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 relay agent

About this task

The DSCP value of a packet specifies the priority level of the packet and affects the transmission priority of the packet.

Procedure

1. Enter system view.

system-view

2. Set the DSCP value for DHCPv6 packets sent by the DHCPv6 relay agent.

ipv6 dhcp dscp dscp-value

The default DSCP value is 56.

Specifying a padding mode for the Interface-ID option

About this task

This feature enables the relay agent to fill the Interface-ID option in the specified mode. When receiving a DHCPv6 packet from a client, the relay agent fills the Interface-ID option in the mode and then forwards the packet to the DHCPv6 server.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Specify a padding mode for the Interface-ID option.

ipv6 dhcp relay interface-id { bas [ merge ] | cn-telecom | interface | tr-101 }

By default, the relay agent fills the Interface-ID option with the index of the interface.

Enabling the DHCPv6 relay agent to support Option 79

About this task

If DHCPv6 relay agents exist in the network, the DHCPv6 server needs the MAC address of the DHCPv6 client for authentication or for IPv6 address or prefix assignment. To meet the requirement, enable the DHCPv6 relay agent that the client first passes to support Option 79. This feature allows the DHCPv6 relay agent to learn the MAC address in the client request. When the relay agent generates a Relay-Forward packet for the request, it fills the MAC address of the client in Option 79. The Relay-Forward packet is then forwarded to the DHCPv6 server.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Enable the DHCPv6 relay agent to support Option 79.

ipv6 dhcp relay client-link-address enable

By default, the DHCPv6 relay agent does not support Option 79.

Enabling the DHCPv6 relay agent to advertise IPv6 prefixes

About this task

A DHCPv6 client can obtain an IPv6 prefix through DHCPv6 and use this IPv6 prefix to assign IPv6 address to clients in a downstream network. If the IPv6 prefix is in a different subnet than the IPv6 address of the DHCPv6 client's upstream interface, the clients in the downstream network cannot access the external network. You can enable the DHCPv6 relay agent that is on the same link as the DHCPv6 client to advertise the IPv6 prefix.

This feature enables the DHCPv6 relay agent to generate a routing entry for the IPv6 prefix when it receives a reply message with the IPv6 prefix. The DHCPv6 relay agent advertises this entry to the dynamic routing protocol. After the DHCPv6 client learns this route through the dynamic routing protocol, clients in the downstream network can access the external network.

Prerequisites

Before you perform this task, make sure the DHCPv6 relay agent is enabled to record DHCPv6 relay entries.

Procedure

1. Enter system view.

system-view

2. Enable the DHCPv6 relay agent to advertise IPv6 prefixes.

ipv6 dhcp advertise pd-route

By default, the DHCPv6 relay agent does not advertise IPv6 prefixes.

Configuring DHCPv6 relay security features

Enabling the DHCPv6 relay agent to record relay entries

About this task

This feature enables the DHCPv6 relay agent to automatically record DHCPv6 relay entries after DHCPv6 clients obtain IPv6 addresses or prefixes through DHCPv6. A DHCPv6 relay entry contains the binding between a client's hardware address and IPv6 address or prefix.

Restrictions and guidelines

The DHCP relay agent does not record IP-to-MAC bindings for DHCP clients that use WAN access methods.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Enable the recording of DHCPv6 relay entries.

ipv6 dhcp relay client-information record

By default, the DHCPv6 relay agent does not record relay entries.

Enabling IPv6 release notification

About this task

This feature enables the DHCPv6 relay agent to send a Release message to the DHCPv6 server after it deletes a DHCPv6 relay entry. After the DHCPv6 server receives the message, it reclaims the IPv6 address or prefix and marks the lease as expired.

If you do not enable this feature, the DHCPv6 relay agent will not send a Release message after it deletes a relay entry.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Enable IPv6 release notification.

ipv6 dhcp relay release-agent

By default, IPv6 release notification is disabled.

Enabling client offline detection

About this task

This feature enables the DHCPv6 relay agent to detect the status of ND entries. After an ND entry ages out, the DHCPv6 relay agent considers the client offline and deletes the relay entry for the client. For more information about ND, see "Configuring basic IPv6 settings."

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Enable client offline detection.

ipv6 dhcp client-detect

By default, client offline detection is disabled.

Display and maintenance commands for DHCPv6 relay agent

Execute display commands in any view and reset commands in user view.

Task	Command
Display the DUID of the local device.	display ipv6 dhcp duid
Display DHCPv6 relay entries that record clients' IPv6 address information.	display ipv6 dhcp relay client-information address [ interface interface-type interface-number \| ipv6 ipv6-address ] [ vpn-instance vpn-instance-name ]
Display DHCPv6 relay entries that record clients' IPv6 prefix information.	display ipv6 dhcp relay client-information pd [ interface interface-type interface-number \| prefix prefix/prefix-len ] [ vpn-instance vpn-instance-name ]
Display the DHCPv6 server configuration and status in the DHCPv6 address pool on the DHCPv6 relay agent.	display ipv6 dhcp relay remote-server-info [ vpn-instance vpn-name ] [ slot slot-number ]
Display DHCPv6 server addresses specified on the DHCPv6 relay agent.	display ipv6 dhcp relay server-address [ interface interface-type interface-number ]
Display packet statistics on the DHCPv6 relay agent.	display ipv6 dhcp relay packet statistics [ interface interface-type interface-number ]
Clear DHCPv6 relay entries that record clients' IPv6 address information.	reset ipv6 dhcp relay client-information address [ interface interface-type interface-number \| ipv6 ipv6-address ] [ vpn-instance vpn-instance-name ]
Clear DHCPv6 relay entries that record clients' IPv6 prefix information.	reset ipv6 dhcp relay client-information pd [ interface interface-type interface-number \| prefix prefix/prefix-len ] [ vpn-instance vpn-instance-name ]
Clear packets statistics on the DHCPv6 relay agent.	reset ipv6 dhcp relay packet statistics [ interface interface-type interface-number ]

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DHCPv6 relay agent configuration examples

Example: Configuring DHCPv6 relay agent

Network configuration

As shown in Figure 10, configure the DHCPv6 relay agent on Router A to relay DHCPv6 packets between DHCPv6 clients and the DHCPv6 server.

Router A acts as the gateway of network 1::/64. It sends RA messages to notify the hosts to obtain IPv6 addresses and other configuration parameters through DHCPv6. For more information about RA messages, see "Configuring basic IPv6 settings."

Figure 10 Network diagram

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Procedure

# Specify IPv6 addresses for Ten-GigabitEthernet 2/0/0 and Ten-GigabitEthernet 2/0/1.

<RouterA> system-view

[RouterA] interface ten-gigabitethernet 2/0/1

[RouterA-Ten-GigabitEthernet2/0/1] ipv6 address 2::1 64

[RouterA-Ten-GigabitEthernet2/0/1] quit

[RouterA] interface ten-gigabitethernet 2/0/0

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 address 1::1 64

# Disable RA message suppression on Ten-GigabitEthernet 2/0/0.

[RouterA-Ten-GigabitEthernet2/0/0] undo ipv6 nd ra halt

# Set the M flag to 1 in RA advertisements to be sent on Ten-GigabitEthernet 2/0/0. Hosts that receive the RA messages will obtain IPv6 addresses through DHCPv6.

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 nd autoconfig managed-address-flag

# Set the O flag to 1 in RA advertisements to be sent on Ten-GigabitEthernet 2/0/0. Hosts that receive the RA messages will obtain information other than IPv6 address through DHCPv6.

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 nd autoconfig other-flag

# Enable the DHCPv6 relay agent on Ten-GigabitEthernet 2/0/0 and specify the DHCPv6 server on the relay agent.

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 dhcp select relay

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 dhcp relay server-address 2::2

Verifying the configuration

# Display DHCPv6 server address information on Router A.

[RouterA-Ten-GigabitEthernet2/0/0] display ipv6 dhcp relay server-address

Interface: Ten-GigabitEthernet2/0/0

Server address Outgoing Interface

2::2

# Display packet statistics on the DHCPv6 relay agent.

[RouterA-Ten-GigabitEthernet2/0/0] display ipv6 dhcp relay packet statistics

Packets dropped : 0

Packets received : 14

Solicit : 0

Request : 0

Confirm : 0

Renew : 0

Rebind : 0

Release : 0

Decline : 0

Information-request : 7

Relay-forward : 0

Relay-reply : 7

Packets sent : 14

Advertise : 0

Reconfigure : 0

Reply : 7

Relay-forward : 7

Relay-reply : 0

Configuring the DHCPv6 client

About the DHCPv6 client

With DHCPv6 client configured, an interface can obtain configuration parameters from the DHCPv6 server.

A DHCPv6 client can use DHCPv6 to complete the following functions:

· Obtain an IPv6 address, an IPv6 prefix, or both, and obtain other configuration parameters. If DHCPv6 server is enabled on the device, the client can automatically save the obtained parameters to a DHCPv6 option group. With the obtained IPv6 prefix, the client can generate its global unicast address.

· Support stateless DHCPv6 to obtain configuration parameters except IPv6 address and IPv6 prefix. The client obtains an IPv6 address through stateless IPv6 address autoconfiguration. If the client receives an RA message with the M flag set to 0 and the O flag set to 1 during address acquisition, stateless DHCPv6 starts.

Restrictions and guidelines: DHCPv6 client configuration

Do not configure the DHCPv6 client on the same interface as the DHCPv6 server or the DHCPv6 relay agent.

DHCPv6 client tasks at a glance

To configure a DHCPv6 client, perform the following tasks:

1. (Optional.) Configuring the DHCPv6 client DUID

2. Configuring the DHCPv6 client to obtain IPv6 addresses, IPv6 prefixes and other network parameters

Choose the following tasks as needed:

¡ Configuring IPv6 address acquisition

¡ Configuring IPv6 prefix acquisition

¡ Configuring IPv6 address and prefix acquisition

¡ Configuring acquisition of configuration parameters except IP addresses and prefixes

3. (Optional.) Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 client

Configuring the DHCPv6 client DUID

About this task

The DUID of a DHCPv6 client is the globally unique identifier of the client. The client pads its DUID into Option 1 of the DHCPv6 packet that it sends to the DHCPv6 server. The DHCPv6 server can assign specific IPv6 addresses or prefixes to DHCPv6 clients with specific DUIDs.

Restrictions and guidelines

Make sure the DUID that you configure is unique.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the DHCPv6 client DUID.

ipv6 dhcp client duid { ascii ascii-string | hex hex-string | mac interface-type interface-number }

By default, the interface uses the device bridge MAC address to generate its DHCPv6 client DUID.

Configuring IPv6 address acquisition

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the interface to use DHCPv6 to obtain an IPv6 address and other configuration parameters.

ipv6 address dhcp-alloc [ option-group group-number | rapid-commit ] *

By default, the interface does not use DHCPv6 for IPv6 address acquisition.

Configuring IPv6 prefix acquisition

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the interface to use DHCPv6 to obtain an IPv6 prefix and other configuration parameters.

ipv6 dhcp client pd prefix-number [ option-group group-number | rapid-commit ] *

By default, the interface does not use DHCPv6 for IPv6 prefix acquisition.

Configuring IPv6 address and prefix acquisition

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the interface to use DHCPv6 to obtain an IPv6 address, an IPv6 prefix, and other configuration parameters.

ipv6 dhcp client stateful prefix prefix-number [ option-group option-group-number | rapid-commit ] *

By default, the interface does not use DHCPv6 for IPv6 address and prefix acquisition.

Configuring acquisition of configuration parameters except IP addresses and prefixes

About this task

When a DHCPv6 client has obtained an IPv6 address and prefix, you can configure the following methods for the client to obtain other network configuration parameters:

· Execute the ipv6 address auto command to enable an interface to automatically generate an IPv6 global unicast address and a link-local address. Then stateless DHCPv6 will be triggered when the M flag is set to 0 and the O flag is set to 1 in a received RA message. For more information about the commands, see Layer 3—IP services Command Reference.

· Executing the ipv6 dhcp client stateless enable command on an interface to enable the interface to act as a DHCPv6 client to obtain configuration parameters from a DHCPv6 server.

If you execute both the ip address auto and ipv6 dhcp client stateless enable commands, the interface acts as follows:

· Generate a global unicast address and a link-local address.

· Obtain other configuration parameters from a DHCPv6 server.

Procedure

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Configure the interface to support stateless DHCPv6. Choose the options to configure as needed:

¡ Enable stateless IPv6 address autoconfiguration:

ipv6 address auto

¡ Configure the client to obtain network parameters from DHCPv6 servers:

ipv6 dhcp client stateless enable

By default, the interface does not support stateless DHCPv6.

Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 client

About this task

The DSCP value of a packet specifies the priority level of the packet and affects the transmission priority of the packet.

Procedure

1. Enter system view.

system-view

2. Set the DSCP value for DHCPv6 packets sent by the DHCPv6 client.

ipv6 dhcp client dscp dscp-value

By default, the DSCP value in DHCPv6 packets sent by the DHCPv6 client is 56.

Display and maintenance commands for DHCPv6 client

Execute the display commands in any view, and execute the reset command in user view.

Task	Command
Display the DHCPv6 client information.	display ipv6 dhcp client [ interface interface-type interface-number ]
Display the DHCPv6 client statistics.	display ipv6 dhcp client statistics [ interface interface-type interface-number ]
Clear the DHCPv6 client statistics.	reset ipv6 dhcp client statistics [ interface interface-type interface-number ]

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DHCPv6 client configuration examples

Example: Configuring IPv6 address acquisition

Network configuration

As shown in Figure 11, configure the router to use DHCPv6 to obtain configuration parameters from the DHCPv6 server. The parameters include IPv6 address, DNS server address, domain name suffix, SIP server address, and SIP server domain name.

Figure 11 Network diagram

‌

Prerequisites

Configure the DHCPv6 server before configuring the DHCPv6 client.

Procedure

# Configure Ten-GigabitEthernet 2/0/0 as a DHCPv6 client for IPv6 address acquisition. Configure the DHCPv6 client to support DHCPv6 rapid address assignment. Configure the DHCPv6 client to create a dynamic DHCPv6 option group for saving configuration parameters.

<Router> system-view

[Router] interface ten-gigabitethernet 2/0/0

[Router-Ten-GigabitEthernet2/0/0] ipv6 address dhcp-alloc rapid-commit option-group 1

[Router-Ten-GigabitEthernet2/0/0] quit

Verifying the configuration

# Verify that the DHCPv6 client has obtained configuration parameters from the server.

[Router] display ipv6 dhcp client

Ten-GigabitEthernet2/0/0:

Type: Stateful client requesting address

State: OPEN

Client DUID: 00030001d07e28db74fb

Preferred server:

Reachable via address: FE80::2E0:1FF:FE00:19

Server DUID: 00030001000fe20a0a00

IA_NA: IAID 0x00000a02, T1 50 sec, T2 80 sec

Address: 1:2::2/128

Preferred lifetime 100 sec, valid lifetime 200 sec

Will expire on Mar 27 2014 at 15:35:55 (196 seconds left)

DNS server addresses:

2000::FF

Domain name:

example.com

SIP server addresses:

2:2::4

SIP server domain names:

bbb.com

# After DHCPv6 server is enabled on the device, verify that configuration parameters are saved in a dynamic DHCPv6 option group.

[Router-Ten-GigabitEthernet2/0/0] display ipv6 dhcp option-group 1

DHCPv6 option group: 1

DNS server addresses:

Type: Dynamic (DHCPv6 address allocation)

Interface: Ten-GigabitEthernet2/0/0

2000::FF

Domain name:

Type: Dynamic (DHCPv6 address allocation)

Interface: Ten-GigabitEthernet2/0/0

example.com

SIP server addresses:

Type: Dynamic (DHCPv6 address allocation)

Interface: Ten-GigabitEthernet2/0/0

2:2::4

SIP server domain names:

Type: Dynamic (DHCPv6 address allocation)

Interface: Ten-GigabitEthernet2/0/0

bbb.com

# Verify that the DHCPv6 client has obtained an IPv6 address.

[Router] display ipv6 interface brief

*down: administratively down

(s): spoofing

Interface Physical Protocol IPv6 Address

GigabitEthernet2/0/0 up up 1:1::2

Example: Configuring IPv6 prefix acquisition

Network configuration

As shown in Figure 12, configure the router to use DHCPv6 to obtain configuration parameters from the DHCPv6 server. The parameters include IPv6 prefix, DNS server address, domain name suffix, SIP server address, and SIP server domain name.

Figure 12 Network diagram

‌

Prerequisites

Configure the DHCPv6 server before configuring the DHCPv6 client.

Procedure

# Configure an IPv6 address for Ten-GigabitEthernet 2/0/0 that is connected to the DHCPv6 server.

<Router> system-view

[Router] interface ten-gigabitethernet 2/0/0

[Router-Ten-GigabitEthernet2/0/0] ipv6 address 1::2/48

# Configure Ten-GigabitEthernet 2/0/0 as a DHCPv6 client for IPv6 prefix acquisition. Configure the DHCPv6 client to support DHCPv6 rapid prefix assignment. Configure the DHCPv6 client to assign an ID to the obtained IPv6 prefix and create a dynamic DHCPv6 option group for saving configuration parameters.

[Router-Ten-GigabitEthernet2/0/0] ipv6 dhcp client pd 1 rapid-commit option-group 1

[Router-Ten-GigabitEthernet2/0/0] quit

Verifying the configuration

# Verify that the DHCPv6 client has obtained an IPv6 prefix and other configuration parameters from the DHCPv6 server.

[Router] display ipv6 dhcp client

Ten-GigabitEthernet2/0/0:

Type: Stateful client requesting prefix

State: OPEN

Client DUID: 00030001d07e28db74fb

Preferred server:

Reachable via address: FE80::2E0:1FF:FE00:19

Server DUID: 0003000100e001000000

IA_PD: IAID 0x00000a02, T1 50 sec, T2 80 sec

Prefix: 12:34::/48

Preferred lifetime 100 sec, valid lifetime 200 sec

Will expire on Feb 4 2014 at 15:37:20(80 seconds left)

DNS server addresses:

2000::FF

Domain name:

example.com

SIP server addresses:

2:2::4

SIP server domain names:

bbb.com

# Verify that the client has obtained an IPv6 prefix.

[Router] display ipv6 prefix 1

Number: 1

Type : Dynamic

Prefix: 12:34::/48

Preferred lifetime 100 sec, valid lifetime 200 sec

# After DHCPv6 server is enabled on the device, verify that configuration parameters are saved in a dynamic DHCPv6 option group.

[Router] display ipv6 dhcp option-group 1

DHCPv6 option group: 1

DNS server addresses

Type: Dynamic (DHCPv6 prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

2000::FF

Domain name:

Type: Dynamic (DHCPv6 prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

example.com

SIP server addresses:

Type: Dynamic (DHCPv6 prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

2:2::4

SIP server domain names:

Type: Dynamic (DHCPv6 prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

bbb.com

Example: Configuring IPv6 address and prefix acquisition

Network configuration

As shown in Figure 13, configure the router to use DHCPv6 to obtain configuration parameters from the DHCPv6 server. The parameters include IPv6 address, IPv6 prefix, DNS server address, domain name suffix, SIP server address, and SIP server domain name.

Figure 13 Network diagram

‌

Prerequisites

Configure the DHCPv6 server before configuring the DHCPv6 client.

Procedure

# Configure an IPv6 address for Ten-GigabitEthernet 2/0/0 that is connected to the DHCPv6 server.

<Router> system-view

[Router] interface ten-gigabitethernet 2/0/0

[Router-Ten-GigabitEthernet2/0/0] ipv6 address 1::2/48

# Configure Ten-GigabitEthernet 2/0/0 as a DHCPv6 client for IPv6 address and prefix acquisition. Specify IDs for the dynamic IPv6 prefix and dynamic DHCPv6 option group, and configure the client to support rapid address and prefix assignment.

[Router-Ten-GigabitEthernet2/0/0] ipv6 dhcp client stateful prefix 1 rapid-commit option-group 1

[Router-Ten-GigabitEthernet2/0/0] quit

Verifying the configuration

# Display DHCPv6 client information. The output shows that the DHCPv6 client has obtained an IPv6 address, an IPv6 prefix, and other configuration parameters from the DHCPv6 server.

[Router] display ipv6 dhcp client

Ten-GigabitEthernet2/0/0:

Type: Stateful client requesting address and prefix

State: OPEN

Client DUID: 00030001d07e28db74fb

Preferred server:

Reachable via address: FE80::2E0:1FF:FE00:19

Server DUID: 0003000100e001000000

IA_NA: IAID 0x00000a02, T1 50 sec, T2 80 sec

Address: 1:1::2/128

Preferred lifetime 100 sec, valid lifetime 200 sec

Will expire on Mar 27 2014 at 15:29:34 (198 seconds left)

IA_PD: IAID 0x00000a02, T1 50 sec, T2 80 sec

Prefix: 12:34::/48

Preferred lifetime 100 sec, valid lifetime 200 sec

Will expire on Mar 27 2014 at 15:29:34 (198 seconds left)

DNS server addresses:

2000::FF

Domain name:

example.com

SIP server addresses:

2:2::4

SIP server domain names:

bbb.com

# Display brief IPv6 information for all interfaces on the device. The output shows that the DHCPv6 client has obtained an IPv6 address.

[Router] display ipv6 interface brief

*down: administratively down

(s): spoofing

Interface Physical Protocol IPv6 Address

GigabitEthernet2/0/0 up up 1:1::2

# Display information about the dynamic IPv6 prefix. The output shows that the client has obtained an IPv6 prefix.

[Router] display ipv6 prefix 1

Number: 1

Type : Dynamic

Prefix: 12:34::/48

Preferred lifetime 100 sec, valid lifetime 200 sec

# After DHCPv6 server is enabled on the device, display information about the dynamic DHCPv6 option group. The output shows that a dynamic DHCPv6 option group exists for saving configuration parameters.

[Router] display ipv6 dhcp option-group 1

DHCPv6 option group: 1

DNS server addresses:

Type: Dynamic (DHCPv6 address and prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

2000::FF

Domain name:

Type: Dynamic (DHCPv6 address and prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

example.com

SIP server addresses:

Type: Dynamic (DHCPv6 address and prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

2:2::4

SIP server domain names:

Type: Dynamic (DHCPv6 address and prefix allocation)

Interface: Ten-GigabitEthernet2/0/0

bbb.com

Example: Configuring stateless DHCPv6

Network configuration

As shown in Figure 14, configure Router A to use stateless DHCPv6 to obtain configuration parameters except IPv6 address and IPv6 prefix. Router B acts as the gateway and advertises RA messages periodically.

Figure 14 Network diagram

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Prerequisites

Configure the DHCPv6 server before configuring the DHCPv6 client.

Procedure

1. Configure the gateway Router B:

# Configure an IPv6 address for Ten-GigabitEthernet 2/0/0.

<RouterB> system-view

[RouterB] interface ten-gigabitethernet 2/0/0

[RouterB-Ten-GigabitEthernet2/0/0] ipv6 address 1::1 64

# Set the O flag to 1 in RA advertisements to be sent on Ten-GigabitEthernet 2/0/0. Hosts that receive the RA advertisements will obtain information other than IPv6 address through DHCPv6.

[RouterB-Ten-GigabitEthernet2/0/0] ipv6 nd autoconfig other-flag

# Disable RA message suppression on Ten-GigabitEthernet 2/0/0.

[RouterB-Ten-GigabitEthernet2/0/0] undo ipv6 nd ra halt

2. Configure the DHCPv6 client on Router A:

# Enable stateless IPv6 address autoconfiguration on Ten-GigabitEthernet 2/0/0.

<RouterA> system-view

[RouterA] interface ten-gigabitethernet 2/0/0

[RouterA-Ten-GigabitEthernet2/0/0] ipv6 address auto

With stateless IPv6 address autoconfiguration enabled, but no IPv6 address configured for Ten-GigabitEthernet 2/0/0, Router A generates a link-local address. It sends an RS message to Router B to request configuration information for IPv6 address generation. Upon receiving the RS message, Router B sends back an RA message. After receiving an RA message with the M flag set to 0 and the O flag set to 1, Router A performs stateless DHCPv6 to get other configuration parameters.

Verifying the configuration

# Display the DHCPv6 client information.

[RouterA-Ten-GigabitEthernet2/0/0] display ipv6 dhcp client interface ten-gigabitethernet 2/0/0

Ten-GigabitEthernet2/0/0:

Type: Stateless client

State: OPEN

Client DUID: 00030001000fe2ff0000

Preferred server:

Reachable via address: FE80::213:7FFF:FEF6:C818

Server DUID: 0003000100137ff6c818

DNS server addresses:

1:2:4::5

1:2:4::7

Domain name:

abc.com

# Display the DHCPv6 client statistics.

[RouterA-Ten-GigabitEthernet2/0/0] display ipv6 dhcp client statistics

Interface : Ten-GigabitEthernet2/0/0

Packets received : 1

Reply : 1

Advertise : 0

Reconfigure : 0

Invalid : 0

Packets sent : 5

Solicit : 0

Request : 0

Renew : 0

Rebind : 0

Information-request : 5

Release : 0

Decline : 0

04-Layer 3—IP Services Configuration Guide

DHCPv6 overview

Rapid assignment involving two messages

Address/prefix lease renewal

Protocols and standards

About DHCPv6 relay agent

Restrictions and guidelines: DHCPv6 relay configuration

Restrictions and guidelines

Procedure

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Procedure

About this task

Procedure

About this task

Restrictions and guidelines

Procedure

About this task

Procedure

About this task

Procedure

About this task

Procedure

About this task

Procedure

About this task

Prerequisites

Procedure

About this task

Restrictions and guidelines

Procedure

Enabling IPv6 release notification

About this task

Procedure

About this task

Procedure

Display and maintenance commands for DHCPv6 relay agent

DHCPv6 relay agent configuration examples

Procedure

Verifying the configuration

About this task

Restrictions and guidelines

Procedure

Configuring IPv6 address acquisition

Configuring IPv6 prefix acquisition

About this task

Procedure

About this task

Procedure

Network configuration

Prerequisites

Procedure

Verifying the configuration

Network configuration

Prerequisites

Procedure

Verifying the configuration

Network configuration

Prerequisites

Procedure

Verifying the configuration

Network configuration

Prerequisites

Procedure

Verifying the configuration

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