Bridging and Switching

1. Which of the following is true concerning bridges?

A. They switch frames in hardware.

B. They support half- and full-duplexing.

C. They support one collision domain for the entire bridge.

D. They do only store-and-forward switching.

Answer: D

Bridges support only the store-and-forward switching method.

A and B are done by switches, not bridges. C is incorrect because each port on a bridge or switch is a separate collision domain.

2. With _________ switching, the switch reads the destination MAC address of the frame and immediately starts forwarding the frame.

A. Store-and-forward

B. Cut-through

C. Fragment-free

D. Runtless

Answer: B

With cut-through switching, the switch reads the destination MAC address of the frame and immediately starts forwarding the frame. With A, the entire frame is read and the CRC is checked before further processing. C and

D are the same thing—once the first 64 bytes of the frame are read, the switch begins to forward it.

3. Which of the following is true concerning full-duplexing?

A. It can either send or receive frames, but not both simultaneously.

B. It can be used with hubs.

C. It can be used with 10Base5 cabling.

D. It uses point-to-point connections.

Answer: D

Full duplex connections require point-to-point connections and cannot involve hubs.

A, B, and C are true of half-duplex connections. Functions of Bridging and Switching

4. Which is not one of the three main functions of a layer-2 device?

A. Learning

B. Forwarding

C. Listening

D. Removing loops

Answer: C

Listening is a port state, not one of the three main functions of a layer-2 device.

A, B, and D are the three main functions of a layer-2 device.

5. During the learning function, the switch places addresses and ports in a(n) _________ table.

A. IP address

B. learning

C. CAM

D. memory

Answer: C

During the learning function, the switch places addresses and ports in a CAM table—another term is port address table.

A, B and D are not terms used to describe this table.

6. Which type of traffic is sent to a group of devices?

A. Multicast

B. Unicast

C. Broadcast

D. Groupcast

Answer: A

Multicast traffic is sent to a group of devices.

B is sent to a single device, and C is sent to all devices. D is a nonexistent traffic type.

7. Which type of traffic is not flooded?

A. Multicast

B. Known unicast

C. Broadcast

D. Unknown unicast

Answer: B

Unicast traffic is not flooded if the destination MAC address is in the CAM table.

A, C, and D traffic is always flooded, to maintain the transparency of the layer-2 device.

8. BPDU stands for ____________.

A. Bridge Protocol Description Unicast

B. Bridge Protocol Data Unit

C. Bridge Protocol Description Unit

D. Bridge Protocol Data Unicast

Answer: B

BPDU stands for Bridge Protocol Data Unit.

A and C are incorrect because of the word description, and the fact that BPDUs use multicasts, which also makes D incorrect.

9. BPDUs are generated every __________ seconds.

A. CLICK HERE

Answer: A

2

BPDUs are generated every two seconds.

10. The root switch is the one elected with the __________ __________.

A. Lowest MAC address

B. Highest MAC address

C. Lowest switch ID

D. Highest switch ID

Answer: C

The switch with the lowest switch ID is elected as the root switch.

A and D are incorrect because the decision is based on the switch ID, which includes the switch’s priority and MAC address. D is incorrect because it is the lowest, not the highest.

11. The switch port that is chosen to forward traffic for a segment is called a __________.

A. Root port

B. Alternate port

C. Backup port

D. Designated port

Answer: D

The switch port that is chosen to forward traffic for a segment is called a designated port.

A is the port that the switch uses to reach the root. B is used in RSTP and is a secondary root port, and C is used in RSTP and is a secondary designated port.

12. Which is true concerning a port in a listening state? (Choose all correct answers.)

A. It remains there for 15 seconds.

B. It forwards BPDUs and builds the CAM table.

C. It remains there for 20 seconds.

D. It forwards BPDUs.

Answer: A

A and D. In a listening state, the port processes and forwards BPDUs. A port stays in the listening state for 15 seconds.

B occurs in the learning state. C is the time period for the blocking state.

13. Enter the 1900 switch command to set an interface to autosense the duplexing: _________.

A. CLICK HERE

Answer: A

DUPLEX AUTO

Use the duplex auto command on the interface to set duplexing to autosensing.

14. Enter the switch command to view the CAM table: ___________.

A. CLICK HERE

Answer: A

SHOW MAC-ADDRESS-TABLE

Use the show mac-address-table command to view the CAM table on either switch.

15. Which 1900 command enables port security?

A. port security

B. switchport security

C. port secure

D. switchport port-security

Answer: C

The port secure command enables port security on a 1900 switch.

D is used on the 2950 switch. A and B are nonexistent commands.