Cisco CCNA Basic Switching Concepts Questions and Answers — Questions and Answers
Question 1: A switch receives a frame on its Fa0/1 interface. The source MAC address is 0000.aaaa.aaaa and the destination MAC address is 0000.bbbb.bbbb. The switch has no entry for 0000.bbbb.bbbb in its MAC address table. What action will the switch take?
- Drop the frame.
- Forward the frame out of all interfaces.
- Forward the frame out of all interfaces except the originating port, Fa0/1. (Correct answer)
- Send an ARP request to find the location of the destination MAC address.
Correct answer: Forward the frame out of all interfaces except the originating port, Fa0/1.
When a switch receives a unicast frame with a destination MAC address that is not in its MAC address table, it floods the frame to all ports within the same VLAN except for the port on which it was received. This process is known as unknown unicast flooding. The switch also learns the source MAC address (0000.aaaa.aaaa) and associates it with the incoming port (Fa0/1).
Question 2: Which of the following is a primary benefit of using VLANs in a network?
- To increase the size of a collision domain.
- To eliminate the need for routers.
- To create a single, large broadcast domain.
- To segment the network into multiple broadcast domains. (Correct answer)
Correct answer: To segment the network into multiple broadcast domains.
Virtual LANs (VLANs) are used to logically segment a Layer 2 network. Each VLAN is a separate broadcast domain. This means that broadcast frames sent by a device in one VLAN are only forwarded to other devices within that same VLAN, not to the entire physical network. This improves security, reduces unnecessary traffic, and enhances network performance.
Question 3: A network administrator is concerned about network latency and wants to ensure frames with errors are not propagated through the network. Which switching method should be used?
- Cut-Through
- Fragment-Free
- Store-and-Forward (Correct answer)
- Fast-Forward
Correct answer: Store-and-Forward
The store-and-forward switching method receives the entire frame before making a forwarding decision. This allows the switch to check the Frame Check Sequence (FCS) at the end of the frame for errors. If an error is detected, the frame is dropped. Cut-through methods, like fast-forward and fragment-free, begin forwarding before the entire frame is received and therefore cannot check for all errors.
Question 4: In a switched network, how does a switch populate its MAC address table?
- By sending out discovery packets to all connected devices.
- By examining the destination MAC address of incoming frames.
- By manually configuring static entries for each device.
- By examining the source MAC address of incoming frames. (Correct answer)
Correct answer: By examining the source MAC address of incoming frames.
A switch learns the MAC addresses of connected devices dynamically by inspecting the source MAC address of every frame it receives. It then creates an entry in its MAC address table, associating the source MAC address with the interface on which the frame was received.
Question 5: A network consists of a single 24-port switch. All ports are operating in full-duplex mode. How many collision domains and broadcast domains exist in this network by default?
- 1 collision domain, 24 broadcast domains
- 24 collision domains, 24 broadcast domains
- 1 collision domain, 1 broadcast domain
- 24 collision domains, 1 broadcast domain (Correct answer)
Correct answer: 24 collision domains, 1 broadcast domain
Each port on a switch is a separate collision domain. Therefore, a 24-port switch has 24 collision domains. By default, all ports on a single switch are part of the same broadcast domain (typically VLAN 1). Broadcasts are forwarded out of all ports. Routers or VLANs are required to segment a network into multiple broadcast domains.
Question 6: What is the primary purpose of the Spanning Tree Protocol (STP) in a switched network?
- To dynamically assign VLANs to switch ports.
- To provide a mechanism for inter-VLAN routing.
- To prevent Layer 2 switching loops. (Correct answer)
- To increase the speed of frame forwarding.
Correct answer: To prevent Layer 2 switching loops.
Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. Its primary function is to prevent bridge loops and the broadcast radiation that results from them by blocking redundant paths in a switched network.
Cisco CCNA Basic Switching Concepts Questions and Answers
A switch receives a frame on its Fa0/1 interface.
The source MAC address is 0000.aaaa.aaaa and the destination MAC address is 0000.bbbb.bbbb.
The switch has no entry for 0000.bbbb.bbbb in its MAC address table.
What action will the switch take?