Which address type is used to uniquely identify a device on the local network?

• A. IP address
• B. MAC address
• C. DNS name
• D. Hostname

Answer: (B)

On a local network, devices are identified at the data link layer by their hardware address—the MAC address. This address is embedded in each network interface and is designed to be unique for that device on the local subnet, allowing switches to deliver frames by the destination MAC in the Ethernet frame. IP addresses operate at the network layer and can change over time (for example, via DHCP) or be reused in different networks, so they aren’t guaranteed to uniquely identify a device within the local link. DNS names and hostnames are human-friendly identifiers that resolve to IP addresses and aren’t used to deliver frames on the local network. So the address type that uniquely identifies a device on the local network is the MAC address.