Which of the following LAN devices only operates at the physical layer of the OSI/ISO model?

A.
Switch

B.
Bridge

C.
Hub

D.
Router

Explanation:
A hub is a multiport repeater. Repeaters work at the physical layer and are add-on devices for extending a
network connection over a greater distance.
Incorrect Answers:
A: Basic switches work at the data link layer. Layer 3, layer 4, and other layer switches have more enhanced
functionality than layer 2 switches.
B: A bridge is a LAN device used to connect LAN segments. It works at the data link layer.
D: Routers work at the network layer.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 612