Client Link-Layer Address Option (CLLAO) Updates
RFC6939 specifies a method for DHCPv6 relay agents to insert a Client Link Layer Address Option (CLLAO) in a DHCPv6 Relay-Forward message as informational material for the DHCPv6 server. The server in turn is not required to echo the CLLAO back in its replies. In some cases, however, the DHCPv6 client may be interested to receive the CLLAO, e.g., to determine if there are L2 devices (e.g., L2 proxies) that rewrite the link-layer address. This document discusses updates to RFC6939 to allow the server to echo the CLLAO back to the client.