- (Topic 3)
A network administrator is getting reports of some internal users who cannot connect to network resources. The users slate they were able to connect last week, but not today. No changes have been configured on the network devices or server during the last few weeks. Which of the following is the MOST likely cause of the issue?

1. A. The client DHCP scope is fully utilized
2. B. The wired network is experiencing electrical interference
3. C. The captive portal is down and needs to be restarted
4. D. SNMP traps are being received
5. E. The packet counter on the router interface is high.

Correct Answer: A

- (Topic 3)
A junior network engineer is trying to change the native network ID to a non-default value that can then be applied consistently throughout the network environment. Which of the following
issues is the engineer attempting to prevent?

1. A. DDoS
2. B. ARP spoofing
3. C. VLAN hopping
4. D. Rogue DHCP

Correct Answer: C

VLAN hopping is a type of network attack where an attacker can send or receive traffic from a VLAN that they are not supposed to access. VLAN hopping can allow an attacker to bypass security policies, access sensitive data, or launch other attacks on the network. VLAN hopping can be performed using two methods: double tagging and switch spoofing1.
Double tagging is where the attacker sends a frame with two VLAN tags, one for the native VLAN and one for the target VLAN. The native VLAN is the VLAN that is used for untagged traffic on a trunk port. If the attacker’s access port is in the same VLAN as the native VLAN, the switch will accept the frame and forward it on the trunk port. The switch will remove the first tag, which is the native VLAN, and send the frame with the second tag, which is the target VLAN. The frame will then reach the target VLAN and be processed by the devices in that VLAN.
Switch spoofing is where the attacker sends Dynamic Trunking Protocol (DTP) packets and tries to negotiate a trunk with the switch. DTP is a Cisco protocol that allows switches to automatically form trunks between them. If the switch’s port is configured with the default dynamic auto or dynamic desirable mode, it will accept the DTP packets and form a trunk with the attacker. The attacker will then have access to all VLANs on the trunk.
To prevent VLAN hopping, the junior network engineer is trying to change the native network ID to a non-default value that can then be applied consistently throughout the network environment. This means that the engineer is changing the VLAN that is used for untagged traffic on the trunk ports to a different VLAN than the default VLAN 1. This will prevent double tagging attacks, as the attacker’s access port will not be in the same VLAN as the native VLAN, and the switch will not accept the frames with two tags. The engineer should also disable DTP on the trunk ports and use the switchport nonegotiate command to prevent switch spoofing attacks2.
ReferencesVLAN Hopping - NetworkLessons.comVLAN Hopping on Native VLAN - Cisco Community

- (Topic 3)
A false camera is installed outside a building to assist with physical security. Which of the following is the device assisting?

1. A. Detection
2. B. Recovery
3. C. Identification
4. D. Prevention

Correct Answer: A

- (Topic 3)
A user took a laptop on a trip and made changes to the network parameters while at the airport. The user can access all internet websites but not corporate intranet websites. Which of the following is the most likely cause of the issue?

1. A. Duplicate IP address
2. B. Duplicate SSID
3. C. Incorrect DNS
4. D. Incorrect subnet mask

Correct Answer: C
DNS (Domain Name System) is a service that translates domain names into IP addresses. Corporate intranet websites are usually hosted on private IP addresses that are not accessible from the public internet. Therefore, the user’s laptop needs to use the correct DNS server that can resolve the intranet domain names to the private IP addresses. If the user changed the network parameters at the airport and did not revert them back, the laptop might be using a public DNS server that does not have the records for the intranet websites. This would cause the user to access all internet websites but not corporate intranet websites.
References:
✑ An Overview of DNS - N10-008 CompTIA Network+ : 1.61
✑ DNS Configuration – CompTIA A+ 220-11012
✑ CompTIA Network+ Certification Exam Objectives, page 53

- (Topic 1)
Which of the following is the physical topology for an Ethernet LAN?

1. A. Bus
2. B. Ring
3. C. Mesh
4. D. Star

Correct Answer: D
In a star topology, all devices on a network connect to a central hub or switch, which acts as a common connection point. Ethernet LANs typically use a star topology, with each device connected to a central switch. References:
✑ Network+ N10-008 Objectives: 2.2 Explain common logical network topologies and their characteristics.