CCNA 1 v6.0 Chapter 4: Network Access: Check your Understanding Answers
1. What are the purpose and functions of the physical layer in data networks? (Choose two.)
- Controls how the data is transmitted onto the physical media
- Encodes the data into signals
- Provides logical addressing
- Packages bits into data units
- Controls media access
Explanation: The physical layer controls data transmitted onto the media and provides encoding of the bits. Logical addressing is provided by Layer 3. The packaging of bits and Media Access Control is provided by the data link layer.
2. Which of these statements regarding UTP network cabling are true? (Choose two.)
- Uses light to transmit data
- Susceptible to EMI and RFI
- Commonly used between buildings
- Most difficult type of networking cable to install
- Most commonly used type of networking cable
Explanation: Even though the twists provide some measure of rejection of stray electrical/magnetic signals, it is still subject to EMI and RFI. Because of its relatively low cost and good performance, UDP is still the most common networking media in use.
3. What is the purpose of cladding in fiber-optic cables?
- Cable grounding
- Noise cancellation
- Prevention of light loss
- EMI protection
Explanation: Cladding is the glass that surrounds the core and acts as a mirror. The light pulses propagate down the core, while the cladding reflects the light pulses. This keeps the light pulses contained in the fiber core in a phenomenon known as total internal reflection.
4. Identify the wire colors associated with the pins when building a 568B network cable.
Pin 1 ___________________
Pin 2 ___________________
Pin 3 ___________________
Pin 4 ___________________
Pin 5 ___________________
Pin 6 ___________________
Pin 7 ___________________
Pin 8 ___________________
Explanation: Pin 1 Orange-white
Pin 2 Orange
Pin 3 Green-white
Pin 4 Blue
Pin 5 Blue-white
Pin 6 Green
Pin 7 Brown-white
Pin 8 Brown
The colors for a 568B pinout from pin 1 to pin 8 are a) orange-white, b) orange c) green-white, d) blue, e) blue-white, f) green, g) brown-white, and h) brown.
5. What are the advantages of using fiber-optic cable over copper cable? (Choose three.)
- Copper is more expensive.
- Immunity to electromagnetic interference.
- Careful cable handling.
- Longer maximum cable length.
- Efficient electrical current transfer.
- Greater bandwidth potential.
Explanation: Unlike copper wires, fiber-optic cable can transmit signals with less attenuation and is immune to EMI and RFI. Fiber-optic cables can also be operated at much greater lengths than copper media and with higher bandwidth.
6. What occurs when another wireless device connects to a wireless access point (WAP)?
- The WAP adds an additional channel to support the new client.
- The WAP throughput for all the connected clients decreases.
- The WAP decreases the radio coverage area.
- The WAP will change frequencies to reduce interference caused by the new client.
Explanation: All wireless devices must share access to the airwaves connecting to the wireless access point. This means that slower network performance might occur as more wireless devices access the network simultaneously.
7. If a node receives a frame and the calculated CRC does not match the CRC in the FCS, what action will the node take?
- Drop the frame
- Reconstruct the frame from the CRC
- Forward the frame as it is to the next host
- Disable the interface on which the frame arrives
Explanation: When the frame arrives at the destination node, the receiving node calculates its own logical summary, or CRC, of the frame. The receiving node compares the two CRC values. If the two values are the same, the frame is considered to have arrived intact. If the CRC value in the FCS differs from the CRC calculated at the receiving node, the frame is discarded.
8. What are the contents of the data field in a frame?
- A CRC
- The network layer PDU
- The Layer 2 source address
- The length of the frame
Explanation: The Layer 3 PDU is wrapped with a header and trailer to form the Layer 2 frame.
9. Which of the following is true about the logical topology of a network?
- Is always multiaccess
- Provides the physical addressing
- Is determined by how the nodes in the network are connected
- Defines how frames are transferred from one node to the next
Explanation: Logical topology refers to the way a network transfers frames from one node to the next.
10. Which of the following is a characteristic of contention-based MAC?
- Used in point-to-point topologies.
- Nodes compete for the use of the medium.
- Leaves MAC to the upper layer.
- Each node has a specific time to use the medium.
Explanation: In contention-based access, all nodes compete for the use of the medium but have a plan if there are collisions.