Module 2 - Switching Concepts

Question 1

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.

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

The more interfaces a router has the larger the resulting broadcast domain.

Answer 1

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

Topic 2.2.0 - 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.

Question 2

What is one function of a Layer 2 switch?

Learns the port assigned to a host by examining the destination MAC
address

Forwards data based on logical addressing

Duplicates the electrical signal of each frame to every port

Determines which interface is used to forward a frame based on the destination MAC address

Answer 2

Determines which interface is used to forward a frame based on the destination MAC address

Topic 2.1.0 - 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.

Question 3

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

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.

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.

Answer 3

A switch creates many smaller collision domains, and a hub increases the size of a single collision domain.

Topic 2.2.0 - 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.

Question 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?

Forward the frame out all ports except the port where the frame is received.

Send the frame to the default gateway address.

Drop the frame.

Use ARP to resolve the port that is related to the frame.

Answer 4

Forward the frame out all ports except the port where the frame is received.

Topic 2.1.0 - 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.

Question 5

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

Fast internal switching
Fast port speed
Frame buffering
High port density

Answer 5

Frame buffering

Topic 2.2.0 - 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.

Question 6

Which switching method makes use of the FCS value?

Cut-through
Large frame buffer
Broadcast
Store-and-forward

Answer 6

Store-and-forward

Topic 2.1.0 - 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.

Question 7

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

The speed of each port

The memory space that is allocated to each switch port

The number of available ports

The numbers of hosts that are connected to each switch port

Answer 7

The number of available ports

Topic 2.2.0 - 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.

Question 8

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

The source and destination MAC addresses and the incoming 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

The source MAC address and the incoming port

The source and destination MAC addresses and the outgoing port

Answer 8

The source MAC address and the incoming port

Topic 2.1.0 - 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.

Question 9

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

All modern NICs support both half-duplex and full-duplex communication.

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.

Half duplex has only one channel.

Answer 9

Full duplex allows both ends to transmit and receive simultaneously.

Full duplex increases the effective bandwidth.

Topic 2.2.0 - 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.

Question 10

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

Destination MAC address
Source MAC address
Source IP address
Destination IP address

Answer 10

Source MAC address

Topic 2.1.0 - 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.

Question 11

Which option correctly describes a switching method?

Cut-through: makes a forwarding decision after receiving the entire frame

Store-and-forward: ensures that the frame is free of physical and datalink errors

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

Answer 11

Store-and-forward: ensures that the frame is free of physical and datalink errors

Topic 2.1.0 - 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.

Question 12

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

Access point
Ethernet bridge
Ethernet hub
Router

Answer 12

Router

Topic 2.2.0 - 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.

Question 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.

Answer 13

They hold traffic, thus alleviating network congestion.

Topic 2.2.0 - 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.

Question 14

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

Router
Switch
Hub
Firewall

Answer 14

Switch

Topic 2.2.0 - A switch provides microsegmentation so that no other device competes for
the same Ethernet network bandwidth.