Introduction to Subinterfaces:
Subinterfaces are logical interfaces created on a single physical interface. They are used to enable a router to support multiple networks on a single physical interface.
Use Case for Subinterfaces:
Subinterfaces are commonly used in scenarios where VLANs are implemented. A router with a single physical LAN port can be configured with multiple subinterfaces, each associated with a different VLAN.
This setup allows the router to route traffic between different VLANs.
Example Configuration:
Consider a router with a single physical interface GigabitEthernet0/0 and two VLANs, 10 and 20.
interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 192.168.10.1 255.255.255.0
!
interface GigabitEthernet0/0.20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
The encapsulation dot1Q command specifies the VLAN ID.
Explanation of the Options:
A . A router with only one available LAN port: This is correct. Subinterfaces allow a single physical interface to manage multiple networks, making it essential for routers with limited physical interfaces.
B . A firewall performing deep packet inspection: Firewalls can use subinterfaces, but it is not a requirement for deep packet inspection.
C . A hub utilizing jumbo frames: Hubs do not use subinterfaces as they operate at Layer 1 and do not manage IP addressing.
D . A switch using Spanning Tree Protocol: STP is a protocol for preventing loops in a network and does not require subinterfaces.
Conclusion:
Subinterfaces provide a practical solution for routing between multiple VLANs on a router with limited physical interfaces. They allow network administrators to optimize the use of available hardware resources efficiently.
Reference:
CompTIA Network+ guide detailing VLAN configurations and the use of subinterfaces (see page Ref 9 Basic Configuration Commands).

If the user cannot communicate with 192.168.10.1, they might be on a different subnet. Changing the subnet mask to 255.255.255.0 ensures the user and the file server are in the same subnet.
Breakdown of Options:
A . Changing the IPv4 address to 192.168.10.1 - This would conflict with the server's IP.
B . Changing the subnet mask to 255.255.255.0 - ✅ Correct answer. Ensures both the user and the server are on the same subnet.
C . Changing the DNS servers - DNS does not affect local network connectivity.
D . Changing the physical address - The MAC address does not impact subnet communication.
Reference:
CompTIA Network+ (N10-009) Official Study Guide - Domain 2.4: Explain subnetting and addressing concepts.

An evil twin attack occurs when an attacker creates a fraudulent AP with an SSID very similar (or identical) to the legitimate one. Users may accidentally connect, allowing the attacker to capture traffic and credentials.
A . On-path is the consequence of connecting to the evil twin, not the initial attack itself.
B . Rogue AP is any unauthorized access point, but the key here is the malicious mimicry of a legitimate SSID - specifically an evil twin.
D . Tailgating is a physical social engineering attack, unrelated to Wi-Fi.
Reference (CompTIA Network+ N10-009):
Domain: Network Security - Wireless threats (rogue APs, evil twins).

The symptoms, including high CPU usage and rapidly blinking switch lights, are most likely due to a cable loop in the network causing a broadcast storm, which is overwhelming network resources and disrupting connectivity.

NTP (Network Time Protocol) synchronizes clocks across network devices, ensuring accurate timestamps in logs. This is critical for correlating events across different systems during investigations.
* A. Syslog collects logs but relies on accurate timestamps already present.
* B. SMTP is an email protocol, unrelated to time synchronization.
* C. SNMP is for monitoring and management, not time.
References (CompTIA Network+ N10-009):
* Domain: Network Operations - Time synchronization (NTP), log correlation, security operations.