ITPEC FE Morning October 2020 Question 31
Which of the following is a device that connects multiple LANs by relaying data through the protocol information of the data link layer of the OSI basic reference model?
Explanation
Bridge — relays frames between LANs by the MAC addresses in the data link layer header.
A bridge learns which MAC addresses sit on each of its ports. When a frame arrives, it reads the destination MAC address and forwards the frame only to the segment where that address lives, or discards it if the destination is on the segment it came from. A layer 2 switch is a bridge with many ports.
Answer (a)
Why not others:
- •(b) Gateway — works at the transport layer and above, converting between different protocols, for example between networks with different application protocols
- •(c) Repeater — works at the physical layer: it only regenerates and amplifies the electrical signal and reads no protocol information
- •(d) Router — works at the network layer, forwarding packets between networks by IP address
Key rule: Place each relay device by the header it reads: repeater (physical signal, layer 1), bridge or switch (MAC address, layer 2), router (IP address, layer 3), gateway (layer 4 and above).
Networks · AI-written, may contain errors
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