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 LLC sublayer provides a way for different network-layer protocols to share the same network link. It sits above the MAC and offers a common interface to the network layer, using fields like DSAP/SSAP (and an optional SNAP sublayer) to identify which higher-layer protocol is being carried. That means IPv4 and IPv6 can both run over the same Ethernet link without needing separate media, because the LLC layer multiplexes these protocols over the same data-link service provided by the MAC.

Error detection and addressing are handled by other parts of the data-link layer: the MAC sublayer uses a trailer/Frame Check Sequence for error detection and handles physical-addressing (MAC addresses). Routing frames based on MAC addresses isn’t a function of LLC; routing is performed by switches and network-layer devices using MAC addresses for forwarding, while the LLC simply indicates the higher-layer protocol and provides multiplexing.