Which OSI layer adds the destination MAC address to a PDU during encapsulation?

• A. Network Layer
• B. Data Link Layer
• C. Application Layer
• D. Presentation Layer

Answer: (B)

The Data Link layer handles framing and MAC addressing. When a network-layer packet arrives at this layer, it is encapsulated into a frame by adding a header that includes the destination MAC address and the source MAC address, plus a trailer for error detection. This MAC addressing is used for delivering frames on the local network segment; switches use the destination MAC to forward the frame to the correct device on that LAN. Routing between networks and handling IP addresses are the job of the Network Layer, not the Data Link layer, and higher layers like Application or Presentation deal with data content rather than hardware addressing. So, the destination MAC address is added at the Data Link layer during encapsulation.