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Configuration Guide - IP Service

CloudEngine 12800 and 12800E V200R005C00

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DNS, IP performance optimization, IPv6, DHCPv6, and IPv6 DNS.
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Options Field in a DHCPv6 Message

Options Field in a DHCPv6 Message

The Options field in a DHCPv6 message carries control information and parameters that are not defined in common protocols. If the Options field is configured on a DHCPv6 server, the DHCPv6 server will add the configured Options field to DHCPv6 Reply messages sent to a DHCPv6 client. Figure 8-4 shows the format of the Options field.

Figure 8-4 Format of the Options field

Table 8-4 Description of the Options field





1 byte

Message type


1 byte

Length of the subsequent content in the Options field


Varies depending on the option-len field

Message content

Table 8-5 describes some known DHCPv6 options. For more details about DHCPv6 options, see RFC 3315.

Table 8-5 Description of DHCPv6 Options

Option No.

Option Name



Client Identifier

This option carries a client's DUID.


Server Identifier

This option carries a server's DUID.


Identity Association for Non-temporary Addresses (IA_NA)

This option carries IA_NA and parameters and non-temporary addresses associated with IA_NA. The IA_NA option includes IAID, T1, and T2.

  • IAID: unique identifier of IA_NA
  • T1: the time at which a client sends a request message to the server that allocates the IA_NA address to the client to renew the allocated IA_NA address
  • T2: the time at which a client sends a request message to all reachable servers to renew the current IA_NA address


IA Address

This option specifies the IPv6 address associated with IA_NA.

The IA Address option must be encapsulated into the Options field of the IA_NA option.

The IA Address option contains the IPv6 address, preferred lifetime, and valid lifetime. If the valid lifetime is set to 0xffffffff (infinity), the IPv6 address will be allocated to a client permanently. Therefore, this operation must be carried out with caution.


Option Request

This option carries the option list in a DHCPv6 message.

A client can inform a server of the requested options through the Option Request option in Solicit, Request, Renew, Rebind, Confirm, or Information-request messages.

A server can inform a client of the offered options through the Option Request option contained in Reconfigure messages.



A server can add the Preference option to an Advertise message to control a client's selection of the server.


Relay Message

The Relay Message option in Relay-forward or Relay-reply messages carries DHCPv6 information.


Server Unicast

A server uses the Server Unicast option to inform a client that the client is allowed to send unicast messages to the server.


Status Code

This option carries the status information related to a DHCPv6 message or option in a DHCPv6 message.


Rapid Commit

This option is used to initiate two-message exchange for address allocation. If a client wants to perform Solicit-Reply message exchange, the client adds the Rapid Commit option to the Solicit message.

After the Solicit-Reply message exchange is completed, the server must add the Rapid Commit option to the Reply message in response to the Solicit message.



A relay agent can use the Interface-Id option to indicate the interface that receives messages from a client. If the relay agent receives a Relay-reply message carrying the Interface-Id option, the relay agent uses the interface identified by this option to relay the message to the client.

The server must copy the Interface-Id option in the received Relay-forward message to the Relay-reply message. The Relay-reply message is sent to the relay agent in response to the Relay-forward message.

A server can apply the Interface-Id option to the parameter allocation policy. The interface ID must be kept unchanged. If the interface ID is changed after the relay agent restarts, the server will not effectively use the Interface-Id option in the parameter allocation policy.



This option in messages sent by a DHCPv6 relay agent carries information such as DUIDs, interfaces, and VLANs.



A DHCPv6 relay agent can use the Client-lla option to carry the client's link layer address.



A DHCPv6 relay agent can use the Vss-control option to carry the client's VPN information.

Updated: 2019-04-18

Document ID: EDOC1100039535

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