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CompTIA Network+ (N10-009) - Practice Questions

15 questions for Network+ prep across networking concepts, implementation, operations, security, and troubleshooting.

Cert page: exams/comptia/network-plus/

Question 1

Scenario: Which OSI layer does a router operate at?

A. Layer 4, transport, forwarding by port number B. Layer 3, network, where packets are forwarded by destination IP address C. Layer 7, application, where devices inspect HTTP and DNS requests before forwarding them D. Layer 2, data link, forwarding by MAC address

Answer **Correct: B** **Why:** Routers forward by IP address at layer 3; switches forward by MAC address at layer 2. Knowing the layer is what tells you which address a device uses and therefore which troubleshooting tool applies.

Question 2

Scenario: A host has IP 192.168.10.50 with mask 255.255.255.0.

A. The mask is invalid for a 192.168 address B. The network is 192.168.10.0/24, with 254 usable host addresses C. The network is 192.168.0.0/16, because the first two octets of a private address define the network D. There are 256 usable hosts, because every address in the 192.168.10.0 block can be assigned to a device

Answer **Correct: B** **Why:** 255.255.255.0 is /24, leaving 8 host bits: 256 addresses minus the network and broadcast addresses gives 254 usable. Subnetting arithmetic appears throughout the exam, so practice converting between dotted-decimal masks and CIDR notation fluently.

Question 3

Scenario: TCP versus UDP.

A. They are interchangeable, since each of them guarantees delivery and ordering and they differ only in port numbers B. UDP is more reliable, because it sends each datagram without a handshake and so cannot be delayed by retransmission C. TCP has no ordering, because segments are delivered in whatever order the network happens to carry them D. TCP is connection-oriented with acknowledgment, ordering, and retransmission; UDP is connectionless with lower overhead and no delivery guarantee

Answer **Correct: D** **Why:** UDP suits real-time traffic where a late packet is worse than a lost one: voice, video, DNS queries. TCP's three-way handshake (SYN, SYN-ACK, ACK) is a frequent exam item, as is the port list that goes with each protocol.

Question 4

Scenario: A workstation gets a 169.254.x.x address.

A. It has a public IP, assigned by the ISP because the workstation is directly connected to the internet B. It has a valid static address, which an administrator configured in the 169.254 range for management C. APIPA: it failed to reach a DHCP server, so check DHCP availability, the relay agent, and layer 2 connectivity D. It is on the internet, with a working DHCP lease and gateway, and the problem is DNS resolution

Answer **Correct: C** **Why:** An APIPA address is a self-assigned link-local fallback and a direct symptom of DHCP failure. Because DHCP uses broadcasts, a client on a different subnet from the server needs a relay agent (IP helper), which is the usual cause when one VLAN works and another does not.

Question 5

Scenario: Which DNS record maps a hostname to an IPv4 address?

A. MX, which lists mail servers B. CNAME, which makes one name an alias for another name rather than an address C. A record, mapping a hostname to an IPv4 address D. AAAA record, for IPv6 addresses

Answer **Correct: C** **Why:** An A record is IPv4, AAAA is IPv6, CNAME is an alias to another name, MX routes mail, PTR does reverse lookup, and TXT holds arbitrary text used for SPF and domain verification. Record-type identification is reliably on the exam.

Question 6

Scenario: VLANs are configured and two hosts in different VLANs cannot communicate.

A. Change the cable between the switches B. That is expected; inter-VLAN routing requires a layer 3 device C. The VLANs are broken, so erase the switch configuration D. Add more switches, so that the hosts in each VLAN have another path to reach the other VLAN

Answer **Correct: B** **Why:** VLANs create separate broadcast domains by design, so traffic between them must be routed. A router-on-a-stick uses a trunk with subinterfaces; a layer 3 switch does it with switched virtual interfaces. Trunk ports carry tagged frames (802.1Q); access ports carry one untagged VLAN.

Question 7

Scenario: Which topology change prevents switching loops?

A. Increasing bandwidth on the uplinks, which lets the switches absorb a broadcast storm without dropping frames B. Raising the TTL on Ethernet frames so looping frames expire later C. Adding more links between the same switches, so that traffic is shared across more parallel paths D. Spanning Tree Protocol, which blocks redundant paths yet keeps them available for failover

Answer **Correct: D** **Why:** Without STP, redundant layer 2 links create broadcast storms because frames have no TTL to expire them. STP keeps the redundancy for failover while logically blocking the loop. The symptom is a network that becomes unusable after adding a switch link.

Question 8

Scenario: A user reports slow performance. What is the first troubleshooting step?

A. Identify the problem: gather information, question the user, and find out what changed B. Replace hardware on the user's workstation and switch port, since slow performance is usually a failing component C. Reboot the server that hosts the application, and check whether the user still sees slow performance D. Escalate immediately to the vendor or a tier 3 team, before collecting any detail about the symptoms

Answer **Correct: A** **Why:** The methodology is examinable in order: identify the problem, establish a theory, test it, establish a plan, implement, verify full functionality, and document. "What changed recently" resolves a large share of real incidents before any tool is opened.

Question 9

Scenario: Which command traces the path a packet takes to a destination?

A. traceroute / tracert, which lists each hop on the way to the destination by incrementing the TTL B. ipconfig, which shows the IP address, mask, and gateway configured on the local interfaces C. ping, which tests whether a destination answers ICMP echo requests but does not list hops D. netstat, which lists active connections and listening ports on the local host

Answer **Correct: A** **Why:** Traceroute reveals where a path breaks by incrementing TTL and recording each responding hop. `ping` tests reachability, `netstat` shows connections and listening ports, and `nslookup` or `dig` test name resolution specifically.

Question 10

Scenario: Cable choice for a 100-metre run in an environment with heavy electrical interference.

A. Fiber optic, which is immune to electromagnetic interference B. Any cable, because the interference limit applies only to runs longer than the 100-metre maximum C. Coaxial, which is thicker and so reaches farther than twisted pair at the same interference level D. Unshielded twisted pair, which cancels interference through the twists in each pair at 100 metres

Answer **Correct: A** **Why:** Fiber is immune to EMI and exceeds copper's 100-metre limit. Shielded twisted pair is the copper mitigation when fiber is not practical. Single-mode fiber goes farther than multimode; multimode is cheaper for short runs.

Question 11

Scenario: Which addresses are reserved for private use?

A. 169.254.0.0/16, the range a host falls back to when no DHCP server answers B. 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 C. 1.1.1.1, a public DNS resolver D. 8.8.8.8, a public DNS resolver address that is routable on the internet

Answer **Correct: B** **Why:** These RFC 1918 ranges are not routable on the internet and require NAT for outbound access. 169.254.0.0/16 is the separate link-local APIPA range. Recognizing the middle range's odd /12 boundary (172.16 through 172.31) is a common exam catch.

Question 12

Scenario: A wireless network must authenticate users against a central directory rather than a shared passphrase.

A. WPA2 or WPA3-Enterprise with 802.1X and a RADIUS server backed by the directory B. WPA3-Personal, with a shared passphrase C. An open network with a captive portal D. WEP with a long key, which is easy to rotate but is the only option on very old access points

Answer **Correct: A** **Why:** Enterprise mode gives per-user credentials, so removing one user does not require rotating a shared key. Personal mode uses a pre-shared key. WEP is broken and should never appear in a correct answer.

Question 13

Scenario: Which device operates at layer 7 and can inspect application content?

A. A media converter, which changes the signal between copper and fiber cabling at layer 1 B. A layer 2 switch, which forwards frames by destination MAC address and sees no application data C. A next-generation firewall or application-layer proxy D. A hub, which repeats every signal to all ports at layer 1 and cannot inspect any content

Answer **Correct: C** **Why:** Traditional firewalls filter on IP, port, and protocol; next-generation firewalls add application awareness, user identity, and intrusion prevention. A load balancer can also operate at layer 7, routing by URL path or hostname.

Question 14

Scenario: Network documentation must support future troubleshooting.

A. Nothing is needed, because the devices store their own configuration and administrators can read it when needed B. A single spreadsheet of IP addresses C. Physical and logical diagrams, an IP address plan, cable labels, configuration backups, and a change log D. Diagrams alone, drawn once at installation, since the topology does not change after that point in the life of the site

Answer **Correct: C** **Why:** The distinction the exam draws is physical (where cables and devices are) versus logical (how traffic flows, VLANs, subnets, routing). Configuration backups are what turn a failed device into a swap rather than a rebuild.

Question 15

Scenario: High availability is required for the default gateway.

A. Two gateways with manual failover, where an administrator changes each client's gateway address after an outage B. A second internet link, which adds a path out but leaves clients pointing at a single gateway address C. More bandwidth on the gateway uplink, which reduces congestion but does not remove the single gateway D. A first-hop redundancy protocol such as HSRP or VRRP presenting a virtual IP

Answer **Correct: D** **Why:** FHRPs let two routers share a virtual IP and MAC so clients never change their gateway setting on failover. Pair it with redundant links and link aggregation (LACP) for a design with no single point of failure at the edge.

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