Dell SmartFabric OS10 User Guide Release 10.5.3

DHCPv6 Relay agent options

When a DHCP client sends a DHCPv6 request, the relay agent adds the DHCPv6 relay agent options to the request. The relay agent then sends the request to the DHCP server. The DHCP server reads the relay agent options information in the packet and uses these options to uniquely determine the defined policy based on which IPv6 addresses are assigned to the clients. The DHCPv6 server uses these options to determine the policy associated with the configuration parameters such as DNS Server, SIP Server, and so on. The DHCPv6 server replies to the relay agent with these options. Upon receipt of the response from the DHCP server, the relay agent strips the DHCPv6 agent options from the packet before sending it to the client.

Following DHCPv6 relay agent options are supported:

• DHCPv6 interface-ID option (option 18).
• remote-id: This sub option contains the system identification. DUID based on system MAC address is used by default for this option. For example: 00:04:89:76:62:78.

DHCPv6 interface-ID option (option 18).

The DHCPv6 interface-ID option (option 18) is used to specify the interface on which the DHCPv6 client message is received. This option is similar to the DHCPv4 relay option 82 sub-option 1 circuit-id. The DHCPv6 server uses the interface-ID option value for the parameter assignment corresponding to the clients. You can configure interface description and the prefix to be used for the interface-ID option. The prefix and the interface description are separated by a colon (:).

The interface description is a combination of VLAN and port information. By default, the interface name is used for the interface description. The VLAN name and the port name are separated by a hyphen (-). You can optionally configure the customized string for each interface using textual descriptions.

The prefix is an optional parameter to be configured globally. You can configure the hostname and VRF name or customized string as prefix. Optionally, you can also configure DHCPv6 hostname. For example, Prefix:<VLAN name>-<Port name>

Interface-ID (option 18) option is disabled by default in the DHCPv6 relay agent.

DHCPv6 Remote-ID Option (option 37)

The DHCPv6 remote-ID option (option 37) is used to specify the remote host identification in the RELAY-FORWARD packet to the DHCPv6 server. This option is similar to the DHCPv4 relay option 82 sub option 2 remote-id. The remote-ID field contains vendor specific enterprise-number and DHCPv6 relay agent DUID by default. The system uses 674 as the enterprise-number. The DHCPv6 server uses this option to select parameters based on the DHCPv6 relay agent.

The remote identification is configured globally. By default, DHCPv6 relay agent type 3 DUID (system mac) is used as remote-ID value. You can optionally configure a customized string to be used. In VLT cases, VLT MAC address is used to generate DUID.

The prefix is an optional parameter to be configured globally. You can configure hostname and VRF name or customized string as prefix. Optionally, you can also configure DHCPv6 hostname.

The prefix and the remote identification are separated by the colon ( : ). For example, prefix : Remote Identification

Remote-ID (option 37) option is disabled by default in the DHCPv6 relay agent.

Restrictions and Limitations

If there is a mismatch in the interface-ID option between the VLT peers, the DHCPv6 client originated packet is dropped and a log is created to indicate the interface-ID option mismatch.

If there is a mismatch in the remote-ID option between the VLT peers, the DHCPv6 client originated packet is dropped and a log is created to indicate the remote-ID option mismatch.

If DHCPv6 hostname is configured for prefix, then Dell Networking recommendeds to configure the same hostname for both the VLT peers.