4.5.3 Ethernet Switching Quiz Answers

Networking Devices and Initial Configuration Module 4.5.3 Ethernet Switching Quiz Answers

1. What is encapsulated into the data field of an Ethernet frame?

  • the Layer 3 PDU
  • a cyclic redundancy check value
  • the encoded physical layer bits
  • the source and destination MAC addresses

Explanation: An Ethernet frame has several fields, one of which is the data field. The data field contains the Layer 3 PDU that is sent down the protocol stack from the network layer.

2. What is the length restriction of the data field in an Ethernet frame?

  • between 0 to 1500 bytes
  • between 46 to 1500 bytes
  • between 46 to 1518 bytes
  • between 46 to 1522 bytes

Explanation: The data field in an Ethernet frame contains the Layer 3 PDU, or an IP packet. This field has the minimum length of 46 bytes and maximum length of 1500 bytes. If the Layer 3 PDU is smaller than 46 bytes, padding is added to meet the minimum length requirement.

3. Refer to the exhibit. What is the MAC address of this computer?

  • 00-01-00-01-15-15-BD-53-48-5B-39-A6-0F-3A
  • 87-52-25-78-0F-3A
  • fe80::740c:63a6:e9df:c700
  • fec0:0:0:ffff::1

Explanation: The MAC address is the physical address of the computer expressed as 12 hexadecimal digits.

4. Which Ethernet sublayer is used to control network access using CSMA/CD?

  • LLC
  • MAC
  • data link
  • physical

Explanation: The two Ethernet sublayers are LLC and MAC. LLC manages communications with the upper layers. MAC is the lower sublayer and is responsible for encapsulating the data and getting it onto the network media. In order to get the data onto the media, a specific process must be used. Ethernet uses the CSMA/CD process.

5. What addressing information is recorded by a switch to build its MAC address table?

  • the destination Layer 3 address of incoming packets
  • the destination Layer 2 address of outgoing frames
  • the source Layer 3 address of outgoing packets
  • the source Layer 2 address of incoming frames

Explanation: A switch builds a MAC address table by inspecting incoming Layer 2 frames and recording the source MAC address found in the frame header. The discovered and recorded MAC address is then associated with the port used to receive the frame.

6. What important information is examined in the Ethernet frame header by a Layer 2 device in order to forward the data onward?

  • source MAC address
  • source IP address
  • destination MAC address
  • Ethernet type
  • destination IP address

Explanation: The Layer 2 device, such as a switch, uses the destination MAC address to determine which path (interface or port) should be used to send the data onward to the destination device.

7. What happens to runt frames received by a Cisco Ethernet switch?

  • The frame is dropped.
  • The frame is returned to the originating network device.
  • The frame is broadcast to all other devices on the same network.
  • The frame is sent to the default gateway.

Explanation: In an attempt to conserve bandwidth and not forward useless frames, Ethernet devices drop frames that are considered to be runt (less than 64 bytes) or jumbo (greater than 1500 bytes) frames.

8. What is indicated by the 100 in the 100BASE-T standard?

  • meters
  • feet
  • megabits per second
  • twists per meter

Explanation: 100BASE-T is an Ethernet standard that translates to 100 megabits per second, baseband transmission, and twisted pair cable​.

9. Which three fields are found in an 802.3 Ethernet frame? (Choose three.)

  • source physical address
  • source logical address
  • media type identifier
  • frame check sequence
  • destination physical address
  • destination logical address

Explanation: The fields of an Ethernet frame are the preamble, destination and source address, length, data, and FCS.

10. Match the components in the notation 100Base-T to the specification.

Explanation: Place the options in the following order:

BASE baseband transmission
T twisted-pair cable
100 speed in Mbps

11. Which two characteristics describe Ethernet technology? (Choose two.)

  • It is supported by IEEE 802.3 standards.
  • It is supported by IEEE 802.5 standards.
  • It typically uses an average of 16 Mbps for data transfer rates.
  • It uses unique MAC addresses to ensure that data is sent to the appropriate destination.
  • It uses a ring topology.

Explanation: The 802.3 Ethernet standard specifies that a network implement the CSMA/CD access control method. Each node on the network has a unique MAC address for communication purposes.

12. What will a host on an Ethernet network do if it receives a frame with a unicast destination MAC address that does not match its own MAC address?

  • It will discard the frame.
  • It will forward the frame to the next host.
  • It will remove the frame from the media.
  • It will strip off the data-link frame to check the destination IP address.

Explanation: In an Ethernet network, each NIC in the network checks every arriving frame to see if the destination MAC address in the frame matches its own MAC address. If there is no match, the device discards the frame. If there is a match, the NIC passes the frame up to the next OSI layer.


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