Which statement about the LLC sublayer is true?

• A. It enables IPv4 and IPv6 to utilize the same network interface and media.
• B. It detects transmission errors using a trailer.
• C. It manages Ethernet addressing at the physical layer.
• D. It routes frames based on MAC addresses.

Answer: (A)

The main idea is that the Logical Link Control (LLC) sublayer provides a way for multiple network-layer protocols to share the same data link. In Ethernet, the data-link layer is split into the MAC sublayer and LLC. LLC uses service access points (DSAP/SSAP) to identify which network-layer protocol is carrying the payload, so both IPv4 and IPv6 can be carried on the same Ethernet link over the same network interface and media. The MAC sublayer handles the actual frame transmission, physical addressing, and error detection with the Frame Check Sequence trailer. Because of that division of labor, LLC isn’t responsible for error detection or for addressing at the MAC level, nor does it perform routing. That’s why the statement describing LLC as enabling IPv4 and IPv6 to share the same interface and media is the best fit.