DUID-LLT is defined as which of the following?

• A. Link-layer address plus time - generated and stored at startup
• B. Assigned by Vendor Based on Enterprise Number
• C. Link-layer - generally used if network interface is permanent or unchangeable
• D. 128-bit Universally Unique Identifier

Answer: (A)

In DHCPv6, a DUID identifies a client, and DUID-LLT specifically uses the link-layer (MAC) address plus a time value. It is generated at startup and stored in non-volatile memory so the same identifier is reused after reboots. This makes it stable yet unique across restarts. The other options refer to different DUID types: vendor-based (DUID-EN), a plain link-layer only (DUID-LL), or a 128-bit UUID (DUID-UUID).