As a CCNA candidate, you must know the various layers of the OSI model. At which layers of the OSI Model do Wide Area Networks operate in? (Choose two)

A. Physical Layer
B. Datalink Layer
C. Network Layer
D. Session Layer
E. Transport Layer
F. Presentation Layer
G. Application Layer

Answer: A, B

Explanation:

A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower two layers of the OSI reference model: the physical layer and the data link layer as shown below.
                                           OSI Layers                            WAN Specifications

Note: Occasionally WAN's would also be considered to operate at layer 3, but since this
question asked for only 2 chopices layers 1 and 2 are better choices.