Solution for Client Identification in DHCPv6 for Layer 2 Aggregation | Cisco CCIE Exam

A.

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In this scenario, a Layer 2 aggregation network is deployed via IEEE 802.1D and has multiple nodes connected to a single link. The DHCPv6 server is unable to recognize how the clients are attached to the network. To provide client identification to the DHCPv6 server, one of the following solutions can be used:

A. LDRA (Link-Layer Discovery and Advertisement Protocol) - This protocol is used to provide information about the link-layer topology to network devices. It allows nodes to advertise their presence and capabilities on a link, and also enables them to discover other nodes on the link. However, LDRA does not provide any client identification to the DHCPv6 server.

B. Broadband Forum Trunk N 1 - This is a specification that defines the behavior of a DSL access multiplexer (DSLAM) in a broadband network. It includes a method for identifying individual clients by their port numbers, but it is specific to DSL access networks and may not be applicable in this scenario.

C. DHCPv6 relay agent - A DHCPv6 relay agent is used to forward DHCPv6 messages between clients and servers that are on different networks. It can be used to provide client identification to the DHCPv6 server by adding option 18 (Interface-ID) to the DHCPv6 message. This option includes information about the interface on which the client is connected, which can be used to identify the client.

D. DHCP snooping - DHCP snooping is a security feature that can be used to prevent unauthorized DHCP servers from providing IP addresses to clients on the network. It can also be used to provide client identification to the DHCPv6 server by inspecting DHCPv6 messages and associating them with the interface on which they were received. This information can then be used to identify the client.

Therefore, the correct answer is either C or D, depending on the specific requirements and constraints of the network.