Which method begins the forwarding process after the destination MAC address of an incoming frame and the egress port have been determined?

CCNAv2 (v5.0) Chapter 1 QUIZ Answers

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1 Which function is supplied by the access layer in a three-layer network design?

high-speed connectivity routing application of policies

network access *

2 Which statement is true about broadcast and collision domains?

Adding a router to a network will increase the size of the collision domain. The size of the collision domain can be reduced by adding hubs to a network. The more interfaces a router has the larger the resulting broadcast domain.

Adding a switch to a network will increase the size of the broadcast domain. *

3 When an appropriate switch form factor for a network is being determined, what should be selected when fault tolerance and bandwidth availability are desired but the budget is limited?

stackable switch * non-stackable switch fixed configuration switch

modular switch

4 What are the three layers of the switch hierarchical design model? (Choose three.)

access * data link

core *

distribution *

5 Which cost-effective physical network topology design is recommended when building a three-tier campus network that connects three buildings?​

bus mesh

extended star *

6 Which two characteristics describe a converged network? (Choose two.)

decreased service calls
support of voice and video both using the same switch * separate wiring infrastructure for voice and video traffic

affordability for small and medium businesses *

7 Which service is provided by an automated attendant feature on a converged network?

point-to-point video
call routing * IT management interface

video conferencing

8 When the appropriate switch form factor for a network is being determined, what type of switch should be selected when future expansion is important and cost is not a limiting factor?

stackable switch 1 rack unit switch fixed configuration switch

modular switch *

9 Which option correctly describes a switching method?

cut-through: makes a forwarding decision after receiving the entire frame store-and-forward: forwards the frame immediately after examining its destination MAC address cut-through: provides the flexibility to support any mix of Ethernet speeds

store-and-forward: ensures that the frame is free of physical and data-link errors*

10

Refer to the exhibit. A switch receives a Layer 2 frame that contains a source MAC address of 000b.a023.c501 and a destination MAC address of 0050.0fae.75aa. Place the switch steps in the order they occur. 

occurs first -> Correct Answer The switch adds the source MAC address to the MAC address table.

occurs second -> Because the destination is not known, the switch forwards the frame out all ports except the port through which the frame arrived.

11

Refer to the exhibit. The PC that is attached to port Fa0/1 is sending a packet that has the destination MAC address of 0050.0fae.299c. Based on the current S1 MAC address table, what will S1 do first when the packet arrives at the switch?

forward the data to S2 broadcast an ARP request to all S1 ports except port Fa0/1

add the MAC address of the PC that is attached to Fa0/1 to the MAC address table *

broadcast the data to all S1 ports that have attached end devices, except the Fa0/1 port

12 Which switching mode describes a switch that transfers a frame as soon as the destination MAC address is read?

fragment-free
cut-through * store-and-forward

latency forwarding

13 Which two statements about Layer 2 Ethernet switches are true? (Choose two.)

Layer 2 switches prevent broadcasts.
Layer 2 switches have multiple collision domains. * Layer 2 switches route traffic between different networks. Layer 2 switches decrease the number of broadcast domains.

Layer 2 switches can send traffic based on the destination MAC address. *

1. Which statement is true about broadcast and collision domains?

• The size of the collision domain can be reduced by adding hubs to a network.
• Adding a switch to a network will increase the size of the broadcast domain.
• Adding a router to a network will increase the size of the collision domain.
• The more interfaces a router has the larger the resulting broadcast domain.

Explanation: A switch that receives a broadcast frame will forward the frame out all other interfaces, including interfaces that connect to other switches. These switches will also perform the same forwarding action. By adding more switches to the network, the size of the broadcast domain increases.

2. What is one function of a Layer 2 switch?

• forwards data based on logical addressing
• determines which interface is used to forward a frame based on the destination MAC address
• duplicates the electrical signal of each frame to every port
• learns the port assigned to a host by examining the destination MAC address

Explanation: A switch builds a MAC address table of MAC addresses and associated port numbers by examining the source MAC address found in inbound frames. To forward a frame onward, the switch examines the destination MAC address, looks in the MAC address for a port number associated with that destination MAC address, and sends it to the specific port. If the destination MAC address is not in the table, the switch forwards the frame out all ports except the inbound port that originated the frame.

3. What is the significant difference between a hub and a Layer 2 LAN switch?

• A hub divides collision domains, and a switch divides broadcast domains.
• Each port of a hub is a collision domain, and each port of a switch is a broadcast domain.
• A switch creates many smaller collision domains, and a hub increases the size of a single collision domain.
• A hub forwards frames, and a switch forwards only packets.

Explanation: Hubs operate only at the physical layer, forwarding bits as wire signals out all ports, and extend the collision domain of a network. Switches forward frames at the data link layer and each switch port is a separate collision domain, and thus more, but smaller, collision domains are created. Switches do not manage broadcast domains because broadcast frames are always forwarded out all active ports.

4. What will a Cisco LAN switch do if it receives an incoming frame and the destination MAC address is not listed in the MAC address table?

• Send the frame to the default gateway address.
• Use ARP to resolve the port that is related to the frame.
• Drop the frame.
• Forward the frame out all ports except the port where the frame is received.

Explanation: A LAN switch populates the MAC address table based on source MAC addresses. When a switch receives an incoming frame with a destination MAC address that is not listed in the MAC address table, the switch forwards the frame out all ports except for the ingress port of the frame. When the destination device responds, the switch adds the source MAC address and the port on which it was received to the MAC address table.

5. Which switch characteristic helps alleviate network congestion when a 10 Gbps port is forwarding data to a 1 Gbps port?

• high port density
• fast port speed
• fast internal switching
• frame buffering

Explanation: The large frame buffers on a switch hold the ingress traffic until such time that the slower egress port can transmit the data. This reduces the number of dropped frames and alleviates network congestion.

6. Which switching method makes use of the FCS value?

• broadcast
• large frame buffer
• store-and-forward
• cut-through

Explanation: The store-and-forward method performs error checking on the frame using the frame-check sequence (FCS) value before sending the frame. The FCS value is the last field in the frame.

7. What does the term “port density” represent for an Ethernet switch?

• the memory space that is allocated to each switch port
• the number of available ports
• the speed of each port
• the numbers of hosts that are connected to each switch port

Explanation: The term port density represents the number of ports available in a switch. A one rack unit access switch can have up to 48 ports. Larger switches may support hundreds of ports.

8. Which information does a switch use to keep the MAC address table information current?

• the source MAC address and the incoming port
• the source and destination MAC addresses and the incoming port
• the source and destination MAC addresses and the outgoing port
• the destination MAC address and the incoming port
• the source MAC address and the outgoing port
• the destination MAC address and the outgoing port

Explanation: To maintain the MAC address table, the switch uses the source MAC address of the incoming packets and the port that the packets enter. The destination address is used to select the outgoing port.

9. Which two statements are true about half-duplex and full-duplex communications? (Choose two.)

• Half duplex has only one channel.
• Full duplex increases the effective bandwidth.
• Full duplex allows both ends to transmit and receive simultaneously.
• Full duplex offers 100 percent potential use of the bandwidth.
• All modern NICS support both half-duplex and full-duplex communication.

Explanation: Full-duplex communication allows both ends to transmit and receive simultaneously, offering 100 percent efficiency in both directions for a 200 percent potential use of stated bandwidth. Half-duplex communication is unidirectional, or one direction at a time. Gigabit Ethernet and 10 Gb/s NICs require full duplex to operate, and do not support half-duplex operation.

10. Which type of address does a switch use to build the MAC address table?

• source IP address
• source MAC address
• destination MAC address
• destination IP address

Explanation: When a switch receives a frame with a source MAC address that is not in the MAC address table, the switch will add that MAC address to the table and map that address to a specific port. Switches do not use IP addressing in the MAC address table.

11. Which option correctly describes a switching method?

• cut-through: makes a forwarding decision after receiving the entire frame
• cut-through: provides the flexibility to support any mix of Ethernet speeds
• store-and-forward: forwards the frame immediately after examining its destination MAC address
• store-and-forward: ensures that the frame is free of physical and data-link errors

Explanation: Store-and-forward switching performs an error check on an incoming frame after receiving the entire frame on the ingress port. Switches which use this method have the flexibility to support any mix of Ethernet speeds. The cut-through method begins the forwarding process after the destination MAC address of an incoming frame is looked up and the egress port has been determined.

12. Which network device can serve as a boundary to divide a Layer 2 broadcast domain?

• router
• Ethernet hub
• access point
• Ethernet bridge

Explanation: Layer 1 and 2 devices (LAN switch and Ethernet hub) and access point devices do not filter MAC broadcast frames. Only a Layer 3 device, such as a router, can divide a Layer 2 broadcast domain.

13. What is the purpose of frame buffers on a switch?

• They execute checksum values before transmission.
• They provide temporary storage of the frame checksum.
• They hold traffic, thus alleviating network congestion.
• They provide a basic security scan on received frames.

Explanation: Switches have large frame buffers that allow data waiting to be transmitted to be stored so the data will not be dropped. This feature is beneficial especially if the incoming traffic is from a faster port than the egress port used for transmitting.

14. Which network device can be used to eliminate collisions on an Ethernet network?

Explanation: A switch provides microsegmentation so that no other device competes for the same Ethernet network bandwidth.