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Switches

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Switches are networking devices that connect devices together on a computer network and use packet switching to forward data to their destination. They work at the Data Link Layer (Layer 2) of the OSI model. Switches manage network traffic by maintaining a MAC address table that they use to filter and forward traffic only to the intended recipients, reducing overall network collisions and congestion. They can be managed or unmanaged; managed switches offer more features such as virtual LANs (VLANs) whereas unmanaged switches have pre-configured settings with limited functionality. These devices can be easily expanded to accommodate more network devices as the network grows, providing efficient traffic management.

Guide on Network Switches | CompTIA Network+

Network Switches form a crucial part of any network infrastructure, playing a key role in the transmission and reception of data packets.

What it is: A network switch is a device that connects devices on a computer network by using packet switching to receive, and forward data to the destination device.

How it works: The switch receives incoming data from one of its ports and then forwards the data to the correct device using the device's MAC address. This helps in keeping the network organized and preventing data frames from being forwarded to unnecessary destinations.

Importance: Switches play a vital role in enhancing network efficiency, reducing traffic congestion, and increasing network performance.

Exam Tips: Answering Questions on Switches
1. Understand the basic functionality of a switch and difference between a hub and a switch.
2. Familiarize yourself with the concept of MAC addresses as these are often used in questions relating to how switches forward information.
3. Be familiar with different types of switches such as managed and unmanaged switches.
4. Understand VLANs, as most Exam questions will require knowledge of how Switches can segregate network traffic.

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CompTIA Network+ - Network Devices Example Questions

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Question 1

A network administrator has observed that switch ports are going into an error-disabled state. What could be the cause of this?

Correct Answer: BPDU Guard

The most common cause of switch ports going into an error-disabled state is the protection mechanism known as BPDU (Bridge Protocol Data Units) Guard. BPDU Guard works by placing a port into an error-disabled state when it receives a BPDU. This is done to protect the network from possible loops. A misconfigured or faulty network device can start firing BPDUs across the network and disrupt the network's normal functioning. BPDU Guard protects against this. Port mirroring is a method used for analyzing and debugging data or diagnosing errors within a network. It has nothing to do with ports going into an error-disabled state. QoS settings, or Quality of Service, help to manage packet loss, delay and jitter on your network. Misconfigured QoS settings can cause problems but not specifically make a switch port go into an error-disabled state. VLAN Trunking Protocol is used for managing all configured VLANs across switches in a network. Faults in VTP may lead to communication issues among VLANs but not directly cause switch ports to go into an error-disabled state.

Question 2

You are a network administrator and have recently installed a managed switch. However, the network performance is worse than before. What could be the possible reason?

Correct Answer: Mismatched cable standards

The best answer for the possible reason behind the worse network performance after installing a managed switch is: Mismatched cable standards Explanation: When a managed switch is installed and functioning, but the network performance is worse than before, the most likely cause is using cables that do not meet the required standards for the desired network speeds. For example, if the switch supports Gigabit Ethernet speeds but Cat5 cables are used instead of Cat5e or Cat6, the network performance will be degraded due to the cable limitations. Now, let's examine why the other options are less suitable: Incorrect VLAN configuration As discussed earlier, an incorrect VLAN configuration would more likely result in devices not being able to communicate with each other at all, rather than just a slowdown in performance. Switch is faulty While a faulty switch can cause performance issues, it is less likely in this scenario since the switch is still functioning, and the problem is described as a degradation in performance rather than a complete failure. Power over Ethernet issues PoE issues can indeed cause performance problems for connected devices, but they would typically affect only the specific devices powered by the switch, rather than the entire network's performance.

Question 3

Two switches are experiencing intermittent disconnections in their trunks. As a network administrator, what should you do to resolve this issue?

Correct Answer: Change the native VLAN on both switches to match

The best way to resolve intermittent disconnections in the trunks of two switches is to 'Change the native VLAN on both switches to match'. The native VLAN should be the same on both ends of the trunk link. If they are not the same, VLAN mismatch errors can occur causing intermittent disconnections. As for the other provided answers: 'Enable BPDU Guard' helps to prevent loops but not disconnections, 'Reconfigure QoS settings' has to do with prioritizing traffic and not connectivity, and 'Recheck IP addressing' is related to host connectivity but not trunk links between switches.

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