The MAC address is used by switches for intranet communications and has no meaning outside of that local network.

• A. IP address
• B. subnet mask
• C. HTTP protocol
• D. MAC address

Answer: (D)

MAC addresses are hardware identifiers used at the data-link layer to deliver frames within the same local network. Switches build a table that maps each device’s MAC address to the switch port where that device is reachable, so a frame can be forwarded directly to the destination within the intranet. Outside the local network, MAC addresses aren’t used for routing; when a frame needs to travel to another network, it goes to a gateway, the frame is stripped and re-encapsulated with new MAC addresses on each hop, while the IP header carries the routing information. This is why a MAC address has meaning only on the local network.

IP addresses, subnet masks, and HTTP operate differently: IP addresses are used for routing across networks, subnet masks define the network portion of an IP address, and HTTP is an application-layer protocol for web traffic.