CompTIA Security+ Question J-54

A security technician at a small business is worried about the Layer 2 switches in the network suffering from a DoS style attack caused by staff incorrectly cabling network connections between switches.
Which of the following will BEST mitigate the risk if implemented on the switches?

A. Spanning tree
B. Flood guards
C. Access control lists
D. Syn flood

Answer: A

Explanation:
Spanning Tree is designed to eliminate network ‘loops’ from incorrect cabling between switches. Imagine two switches named switch 1 and switch 2 with two network cables connecting the switches. This would cause a network loop. A network loop between two switches can cause a ‘broadcast storm’ where a broadcast packet is sent out of all ports on switch 1 which includes two links to switch 2. The broadcast packet is then sent out of all ports on switch 2 which includes links back to switch 1. The broadcast packet will be sent out of all ports on switch 1 again which includes two links to switch 2 and so on thus flooding the network with broadcast traffic. The Spanning-Tree Protocol (STP) was created to overcome the problems of transparent bridging in redundant networks. The purpose of STP is to avoid and eliminate loops in the network by negotiating a loop-free path through a root bridge. This is done by determining where there are loops in the network and blocking links that are redundant. Spanning-Tree Protocol executes an algorithm called the Spanning-Tree Algorithm (STA). In order to find redundant links, STA will choose a reference point called a Root Bridge, and then determines all the available paths to that reference point. If it finds a redundant path, it chooses for the best path to forward and for all other redundant paths to block. This effectively severs the redundant links within the network. All switches participating in STP gather information on other switches in the network through an exchange of data messages. These messages are referred to as Bridge Protocol Data Units (BPDUs). The exchange of BPDUs in a switched environment will result in the election of a root switch for the stable spanning-tree network topology, election of designated switch for every switched segment, and the removal of loops in the switched network by placing redundant switch ports in a backup state.

CompTIA Network+ Question A-79

A network topology that utilizes a central device with point-to-point connections to all other devices is which of the following?

A. Star
B. Ring
C. Mesh
D. Bus

Correct Answer: A

Explanation:
A Star network is the most common network in use today. Ethernet networks with computers connected to a switch (or a less commonly a hub) form a star network. The switch forms the central component of the star. All network devices connect to the switch. A network switch has a MAC address table which it populates with the MAC address of every device connected to the switch. When the switch receives data on one of its ports from a computer, it looks in the MAC address table to discover which port the destination computer is connected to. The switch then unicasts the data out through the port that the destination computer is connected to.

CompTIA Network+ Question A-53

A network topology in which all nodes have point to point connections to all other nodes is known as which of the following?

A. Mesh
B. Ring
C. Bus
D. Star

Correct Answer: A

CompTIA Network+ Question A-39

When a client calls and describes a problem with a computer not being able to reach the Internet, in which of the following places of the OSI model would a technician begin troubleshooting?

A. Transport layer
B. Physical layer
C. Network layer
D. Session layer

Correct Answer: B

Explanation:
The bottom layer of the OSI reference model is Layer 1, the physical layer.
The physical layer is the layer that defines the hardware elements of a network. These elements include:
Network Interface Cards Network topology Network cabling
The type of signals used for data transmissions
When troubleshooting a network connectivity issue, the first thing you would check is the computer’s network cabling, the network card etc. In other words, the computer’s physical connection to the network.

CompTIA Network+ Question A-29

A network engineer is dispatched to an employee office to troubleshoot an issue with the employee’s laptop. The employee is unable to connect to local and remote resources. The network engineer flips the laptop’s wireless switch on to resolve the issue. At which of the following layers of the OSI model was the issue resolved?

A. Layer 1
B. Layer 2
C. Layer 3
D. Layer 4
E. Layer 7

Correct Answer: A

Explanation:
The bottom layer of the OSI reference model is Layer 1, the physical layer.
The physical layer is the layer that defines the hardware elements of a network. These elements include:
Network Interface Cards
Network topology Network cabling
The type of signals used for data transmittions
In this question, the network engineer flipped the laptop’s wireless switch on to resolve the issue. The laptop was unable to connect to the wireless network because the wireless network interface card was switched off. Switching the wireless network interface card on enabled the laptop to connect to the wireless network. The wireless network interface card is a physical layer device.

CompTIA A+ Question J-83

Which of the following describes a network topology MOST commonly used in a SOHO switched network?

A. Mesh
B. Hybrid
C. Bus
D. Star

Correct Answer: D