CompTIA Network+ (N10-009)

✅ Option C (Correct) Reasoning: Updating the leadership team on the results of an approved change request after a breach directly aligns with documenting findings, actions, outcomes, and lessons learned. This is the final step in the troubleshooting methodology, ensuring all stakeholders are informed and that knowledge is captured for future prevention.❌ Why the other choices are incorrect:

Option A is incorrect: Establishing a theory of probable cause occurs early in the troubleshooting process, focusing on identifying the root issue. The scenario describes a post-resolution update.

Option B is incorrect: Implementing the solution involves executing the planned fix. The scenario describes an update after the change request was approved and presumably implemented.

Option D is incorrect: Establishing a plan of action comes before implementation, outlining how to resolve the problem. The scenario details communication after the resolution process.

✅ Option D (Correct) Reasoning: 802.1X implements port-based authentication, requiring devices connecting to a network port (like a wall jack) to authenticate before gaining network access. This directly prevents unauthorized users from simply plugging into conference room jacks and accessing company resources. ❌ Why the other choices are incorrect:

Option A is incorrect: Creating a trusted the network but doesn't prevent unauthenticated devices from connecting to a wall jack within that no port-level authentication is enforced.

Option B is incorrect: Disabling unused services is a host security measure that reduces attack surface on servers, but it does not prevent unauthorized physical access to the network through wall jacks.

Option C is incorrect: MAC filtering restricts access based on MAC addresses. However, it can be easily bypassed through MAC spoofing and is administratively complex to manage for dynamic user environments like conference rooms.

✅ Option C (Correct) Reasoning: A /25 CIDR range provides 2^(32-25) = 2^7 = 128 total IP addresses. Subtracting the network and broadcast addresses leaves 126 usable host IP addresses, which perfectly matches the requirement for 126 users, making it the most efficient choice. ❌ Why the other choices are incorrect:

Option A is incorrect: A /23 network has 510 usable hosts, which is inefficiently large for 126 users.

Option B is incorrect: A /24 network provides 254 usable hosts, exceeding the requirement and being less efficient than a /25.

Option D is incorrect: A /26 network only offers 62 usable hosts, which is insufficient for 126 users.

Option E is incorrect: 169.254.0.0/16 is an APIPA range, not suitable for a planned network of 126 users and is highly inefficient in terms of address space.

✅ Option B (Correct) Reasoning: tcpdump is a powerful command-line packet analyzer that captures and displays network traffic on an interface. This allows a technician to directly observe if a server is receiving any network packets, making it highly effective for troubleshooting connectivity issues by verifying traffic flow.❌ Why the other choices are incorrect:

Option A is incorrect: traceroute maps the network path and measures transit delays to a destination, showing hops. It does not display the actual network traffic being received by a server.

Option C is incorrect: nslookup queries DNS servers for name resolution. It does not monitor or display general network traffic being received by the server.

Option D is incorrect: arp displays and modifies the IP-to-MAC address cache for local network resolution. It does not provide insight into whether the server is actively receiving network traffic.

✅ Option B (Correct) Reasoning: OSPFv3 (Open Shortest Path First version 3) is a link-state Interior Gateway Protocol (IGP) specifically designed to support IPv6. It is highly efficient for routing within an internal network by establishing a complete network topology. ❌ Why the other choices are incorrect:

Option A is incorrect: EIGRP (Enhanced Interior Gateway Routing Protocol) does support IPv6 (EIGRP for IPv6), but OSPFv3 is an open-standard protocol explicitly built for IPv6, making it a more universal choice for internal IPv6 routing.

Option C is incorrect: BGP4 (Border Gateway Protocol version 4) is an Exterior Gateway Protocol (EGP), primarily used for routing between different autonomous systems on the internet, not typically for internal routing within a single company network.

Option D is incorrect: iBGP (Internal BGP) is used within a single autonomous system, but BGP itself is an EGP. It is not an optimal or standard choice for typical internal network routing protocol functions like OSPFv3.

✅ Option C (Correct) Reasoning: Inadequate termination, such as untwisting wire pairs excessively before crimping or punching down, disrupts the delicate balance of the twists. These twists are essential for canceling electromagnetic interference between adjacent wire pairs, directly leading to high crosstalk. ❌ Why the other choices are incorrect:

Option A is incorrect: Outside interference from adjacent cabling refers to external electromagnetic interference (EMI), which is different from crosstalk. Crosstalk specifically denotes signal coupling between pairs within the same cable.

Option B is incorrect: Cat 6 cabling is an advanced standard designed to reduce crosstalk and improve signal integrity compared to older categories like Cat 5e, due to its tighter twists and improved construction.

Option D is incorrect: Lack of shielded twisted pair (STP) means the cable is UTP. While STP provides better immunity to external EMI, UTP cables are designed to mitigate crosstalk through their inherent twisted pair design when properly installed and terminated.

✅ Option C (Correct) Reasoning: IP address 192.168.123.232 belongs to Class C. Class C addresses are identified by a first octet ranging from 192 to 223. The first octet '192' clearly places this address in Class C, commonly used for smaller networks.❌ Why the other choices are incorrect:

Option A is incorrect: Class A IP addresses have a first octet ranging from 1 to 126. The address 192.168.123.232 does not start with a Class A octet.

Option B is incorrect: Class B IP addresses have a first octet ranging from 128 to 191. The address 192.168.123.232 does not start with a Class B octet.

Option D is incorrect: Class D IP addresses have a first octet ranging from 224 to 239. These are reserved for multicast communication, not for host addresses.

✅ Option A (Correct) Reasoning: A site-to-site VPN creates a secure, encrypted tunnel between two networks over an untrusted network, such as the internet. This allows secure communication between geographically separated offices or an office and a cloud environment. ❌ Why the other choices are incorrect:

Option B is incorrect: Encrypting data at rest involves technologies like full disk encryption or database encryption, not site-to-site VPNs, which secure data in transit.

Option C is incorrect: Filtering traffic between internal subnets is primarily a function of firewalls or Access Control Lists (ACLs), not the core purpose of a site-to-site VPN.

Option D is incorrect: While applications might use VPNs to access backend resources, a site-to-site VPN's purpose is to connect private networks, not to directly host public-facing applications.

✅ Option D (Correct) Reasoning: Multitenancy is a cloud computing architecture where a single instance of a system or application serves multiple distinct customer organizations (tenants). In public clouds, customers share underlying physical infrastructure while maintaining logical separation of their data and applications.❌ Why the other choices are incorrect:

Option A is incorrect: Elasticity describes the ability to dynamically scale computing resources up or down on demand to meet fluctuating workloads. It does not define shared customer housing.

Option B is incorrect: Hybrid cloud combines public cloud, private cloud, and on-premises infrastructure. It is an architectural model, not the concept of multiple customers sharing a single public cloud data center.

Option C is incorrect: Scalability is the ability of a system to handle an increasing workload by adding resources. It focuses on growth capacity, not the logical isolation of multiple users on shared infrastructure.

✅ Option D (Correct) Reasoning: DNS poisoning, specifically DNS cache poisoning, involves injecting fraudulent DNS records into a DNS server's cache. This causes the server to return incorrect IP addresses for legitimate domain names to its clients, redirecting traffic to malicious sites.❌ Why the other choices are incorrect:

Option A is incorrect: Editing and changing DNS address records directly on a DNS server implies unauthorized administrative access to the server itself, which is a broader compromise, not specific to cache poisoning.

Option B is incorrect: Setting up a malicious DNS server is a rogue server scenario. While it serves false information, DNS poisoning specifically refers to corrupting the cache of an existing legitimate server.

Option C is incorrect: Intercepting client requests and returning false responses describes a Man-in-the-Middle attack. While related to DNS abuse, DNS poisoning is more precise about how the false information enters the DNS infrastructure (i.e., the cache).