CCNA 1 v7 Modules 4 – 7.

What is the purpose of the OSI physical layer?

• controlling access to media

• transmitting bits across the local media

• performing error detection on received frames

• exchanging frames between nodes over physical network media

Answer explanation

The OSI physical layer is responsible for transmitting bits across the local media, ensuring that data is sent as electrical, optical, or radio signals. This is the fundamental role of the physical layer in network communication.

Why are two strands of fiber used for a single fiber optic connection?

• The two strands allow the data to travel for longer distances without degradation.

• They prevent crosstalk from causing interference on the connection.

• They increase the speed at which the data can travel.

• They allow for full-duplex connectivity.

Answer explanation

Using two strands allows for full-duplex connectivity, meaning data can be transmitted and received simultaneously. This enhances communication efficiency compared to a single strand, which can only handle one direction at a time.

Which characteristic describes crosstalk?

• the distortion of the network signal from fluorescent lighting

• the distortion of the transmitted messages from signals carried in adjacent wires

• the weakening of the network signal over long cable lengths

• the loss of wireless signal over excessive distance from the access point

Answer explanation

Crosstalk refers to the distortion of transmitted messages caused by signals from adjacent wires. This interference can lead to data errors, making the second answer choice the correct description of crosstalk.

Which procedure is used to reduce the effect of crosstalk in copper cables?

• requiring proper grounding connections

• twisting opposing circuit wire pairs together

• wrapping the bundle of wires with metallic shielding

• designing a cable infrastructure to avoid crosstalk interference

• avoiding sharp bends during installation

Answer explanation

Twisting opposing circuit wire pairs together helps to cancel out electromagnetic interference, thereby reducing crosstalk in copper cables. This method is effective in maintaining signal integrity.

A network administrator is measuring the transfer of bits across the company backbone for a mission critical financial application. The administrator notices that the network throughput appears lower than the bandwidth expected. Which three factors could influence the differences in throughput?

• the amount of traffic that is currently crossing the network

• the type of traffic that is crossing the network

• the bandwidth of the WAN connection to the Internet

• the latency that is created by the number of network devices that the data is crossing

• the sophistication of the encapsulation method applied to the data

Answer explanation

Throughput can be affected by the amount of traffic on the network, the type of traffic (which may require more processing), and latency introduced by multiple network devices, all of which can reduce effective data transfer rates.

What are two characteristics of fiber-optic cable?

• It is not affected by EMI or RFI.

• Each pair of cables is wrapped in metallic foil.

• It combines the technique of cancellation, shielding, and twisting to protect data.

• It typically contains 4 pairs of fiber-optic wires.

• It is more expensive than UTP cabling is.

Answer explanation

Fiber-optic cables are immune to electromagnetic interference (EMI) and radio frequency interference (RFI), making them reliable for data transmission. Additionally, they are generally more expensive than unshielded twisted pair (UTP) cabling.

What is a primary role of the Physical layer in transmitting data on the network?

• create the signals that represent the bits in each frame on to the media

• provide physical addressing to the devices

• determine the path packets take through the network

• control data access to the media

Answer explanation

The primary role of the Physical layer is to create the signals that represent the bits in each frame and transmit them over the media. This is essential for data transmission in a network.

With the use of unshielded twisted-pair copper wire in a network, what causes crosstalk within the cable pairs?

• the magnetic field around the adjacent pairs of wire

• the use of braided wire to shield the adjacent wire pairs

• the reflection of the electrical wave back from the far end of the cable

• the collision caused by two nodes trying to use the media simultaneously

Answer explanation

Crosstalk in unshielded twisted-pair cables is primarily caused by the magnetic field generated around adjacent wire pairs. This interference can lead to signal degradation, making the correct choice 'the magnetic field around the adjacent pairs of wire'.

What type of cabling is shown?

• STP

• UTP

• coax

• fiber

Answer explanation

The cabling shown is fiber, which is characterized by its use of glass or plastic fibers to transmit data as light. This allows for high-speed data transmission over long distances, unlike STP, UTP, or coaxial cables.

In addition to the cable length, what two factors could interfere with the communication carried over UTP cables?

• crosstalk

• bandwidth

• size of the network

• signal modulation technique

• electromagnetic interference

Answer explanation

Crosstalk occurs when signals from adjacent wires interfere with each other, while electromagnetic interference (EMI) from external sources can disrupt the signal quality in UTP cables. Both significantly affect communication.