CCNA Network Infrastructure and Connectivity Practice Test 18 — 15 Questions

Question 1

A network administrator is configuring a new Windows workstation on a small office network that uses IPv4 addressing. The workstation must be able to communicate with devices on other subnets and resolve hostnames via a company DNS server at 10.10.10.5. The administrator has already set the IP address to 10.10.10.10 and the subnet mask to 255.255.255.0. Which additional parameter must be configured to meet both requirements?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5.. To communicate with devices on other subnets, the workstation needs a default gateway (router) to forward traffic beyond its local subnet. The IP address 10.10.10.10 with subnet mask 255.255.255.0 places it in the 10.10.10.0/24 network, so a default gateway (e.g., 10.10.10.1) is required for inter-subnet routing. Additionally, to resolve hostnames, the DNS server address must be explicitly configured; the company DNS server is at 10.10.10.5. Option A correctly provides both parameters.

Answer

Configure only a DNS server of 10.10.10.5.

Answer

Change the subnet mask to 255.255.0.0 to allow communication across subnets.

Answer

Configure a default gateway of 10.10.20.1 and a DNS server of 10.10.10.5.

Question 2

A junior network engineer is configuring a new Windows 10 workstation to connect to the corporate network. The network uses a /24 subnet mask and has a default gateway of 192.168.1.1. The workstation obtains its IP address automatically from a DHCP server, but the engineer needs to manually set a static IPv4 address of 192.168.1.50 and ensure the workstation can reach the internet. Which configuration step must the engineer take to satisfy these requirements?

Accepted Answer

Set the subnet mask to 255.255.255.0 and the default gateway to 192.168.1.1. A /24 subnet mask (255.255.255.0) matches the network prefix of the default gateway 192.168.1.1, ensuring the workstation can route traffic to the internet via that gateway. Option A fails because a /16 mask (255.255.0.0) does not match the corporate /24 network, causing incorrect network identification and potential routing issues. Option C fails because leaving the default gateway blank means the host cannot reach any network beyond its local subnet, so internet access is impossible. Option D fails because using the host's own IP (192.168.1.50) as the default gateway would cause the host to attempt to route traffic to itself, never reaching the actual gateway.

Answer

Set the subnet mask to 255.255.0.0 and the default gateway to 192.168.1.1

Answer

Set the subnet mask to 255.255.255.0 and leave the default gateway blank

Answer

Set the subnet mask to 255.255.255.0 and the default gateway to 192.168.1.50

Question 3

A network administrator is troubleshooting a wireless connectivity issue in a large office. Users on the 5 GHz band report intermittent disconnections and slow performance, while 2.4 GHz clients are unaffected. The office uses a Cisco 9800 WLC with APs that support 802.11ac Wave 2. The administrator checks the WLC's RF profile and notices a high number of channel utilization reports on channel 36. What is the most likely cause of the problem?

Accepted Answer

Change some APs to use channels 40, 44, or 48 to reduce co-channel interference.. Channel 36 is a 20 MHz channel in the 5 GHz band. When many APs use the same channel (channel 36), they share the same medium, leading to co-channel interference (CCI). This causes intermittent disconnections and slow performance for 5 GHz clients because they must contend for airtime. Spreading APs across non-overlapping channels like 40, 44, or 48 reduces CCI and improves performance.

Answer

Enable DFS channels to avoid radar interference.

Answer

Increase the channel width to 160 MHz to improve throughput.

Answer

Disable the 2.4 GHz radios to force all clients to 5 GHz.

Question 4

Which statement correctly describes a feature of WPA3 security in wireless LANs?

Accepted Answer

WPA3 introduces Simultaneous Authentication of Equals (SAE) to resist offline dictionary attacks.. WPA3 introduces Simultaneous Authentication of Equals (SAE), which uses a Dragonfly key exchange to resist offline dictionary attacks and provide forward secrecy. Option A is wrong because WPA3 does not use or support TKIP encryption; it mandates AES. Option C is wrong because WPA3-Personal uses SAE, not 802.1X/EAP. Option D is wrong because GCMP-256 is only mandatory in the optional WPA3-Enterprise 192-bit security mode, not across all WPA3 deployments; standard WPA3-Personal uses AES-GCMP with 128-bit keys. Option E is wrong because WPA3 requires Protected Management Frames (PMF) by default, unlike WPA2.

Answer

WPA3 uses TKIP encryption for backward compatibility with legacy devices.

Answer

WPA3 relies solely on 802.1X/EAP authentication for both personal and enterprise modes.

Answer

WPA3 mandates the use of GCMP-256 encryption for enhanced security.

Answer

WPA3 makes Protected Management Frames (PMF) optional to support older clients.

Question 5

Which TWO statements accurately describe wireless LAN fundamentals for CCNA 200-301 v2.0? (Choose two.)

Accepted Answer

802.11ac operates only in the 5 GHz frequency band.. 802.11ac (Wi‑Fi 5) operates exclusively in the 5 GHz band, leveraging wider channels (up to 160 MHz) and reduced interference. Option D is correct: WPA3 introduces Simultaneous Authentication of Equals (SAE) for robust password‑based authentication, replacing the weaker WPA2 four‑way handshake. Option A is wrong: 802.11ax (Wi‑Fi 6) supports MU‑MIMO for both uplink and downlink, not only downlink. Option C is wrong: Overlapping channels in the 2.4 GHz band reduce throughput and are not used to maximize availability; instead, non‑overlapping channels (1, 6, 11) are recommended. Option E is wrong: A WLC is typically managed via a web GUI, SSH, or SNMP, not via its console port for routine operations; console access is used for initial setup or troubleshooting.

Answer

802.11ax uses MU‑MIMO only for downlink transmissions.

Answer

Overlapping channels in the 2.4 GHz band are used to maximize non-overlapping channel availability.

Answer

A wireless LAN controller (WLC) is typically managed via its console port for day-to-day operations.

Question 6

A network administrator is troubleshooting a Windows 10 client that cannot reach the internet. The client is connected to a Cisco switch port configured as an access port in VLAN 100. The administrator runs ipconfig on the client and sees an IP address of 169.254.10.15 with a subnet mask of 255.255.0.0. The switch port shows status up/up. What is the most likely cause of the issue?

Accepted Answer

The switch is not configured with an ip helper-address on the VLAN 100 SVI to forward DHCP broadcasts to the DHCP server.. The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when DHCP fails. Since the client is in VLAN 100 and the switch port is up/up, the most likely cause is that the VLAN 100 SVI lacks an ip helper-address command, so DHCP broadcast requests from the client are not forwarded to the DHCP server, leaving the client without a valid IP address.

Answer

The switch port is in err-disabled state due to a spanning-tree loop.

Answer

The client is in the wrong VLAN; the switch should be configured with VLAN 200.

Answer

There is a duplex mismatch between the client and the switch.

Question 7

Which TWO commands can a network technician use on a modern Linux host to verify the IP address configuration and test reachability to a remote server?

Accepted Answer

ip addr. The `ip addr` command (option A) is the modern Linux utility for displaying IP address configuration, replacing the deprecated `ifconfig`. The `ping` command (option D) uses ICMP Echo Request/Reply messages to test Layer 3 reachability to a remote server. `ifconfig` (option B) is deprecated and not expected for current certification exams; `tracert` (option C) is a Windows command; `nslookup` (option E) performs DNS lookups but does not verify IP configuration or connectivity.

Answer

ifconfig

Answer

tracert

Answer

nslookup

Question 8

A network administrator is troubleshooting a Windows 10 client that cannot access a web server at 192.168.1.100. The client has an IP address of 192.168.1.50/24 and can ping its default gateway (192.168.1.1) successfully, but ping to 192.168.1.100 fails. Which command should the administrator run next to verify the client's current network connections and identify potential issues with active sessions?

Accepted Answer

netstat -a. The `netstat -a` command displays all active TCP/UDP connections and listening ports, which is the most direct way to verify current network sessions and identify issues such as blocked ports, half-open connections, or failed connection attempts. While ping failure could result from network-layer filtering (e.g., ACLs blocking ICMP), `netstat -a` reveals whether the client has initiated a TCP connection to 192.168.1.100 and its current state (e.g., SYN_SENT, ESTABLISHED, TIME_WAIT), helping to isolate transport-layer or application-layer problems.

Answer

ipconfig /all

Answer

tracert 192.168.1.100

Answer

ping -t 192.168.1.100

Question 9

A network administrator receives a report that a user on a Windows laptop cannot connect to the internet, although other devices on the same subnet are working. The administrator runs `ipconfig` on the laptop and sees an IP address of 169.254.15.22 with a subnet mask of 255.255.0.0 and no default gateway. Based on this output, what is the most likely cause of the connectivity issue?

Accepted Answer

The DHCP server is unreachable or not responding to the laptop's DHCP request.. The IP address 169.254.15.22 with a subnet mask of 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, which Windows assigns when a DHCP client fails to obtain a lease from a DHCP server. The absence of a default gateway confirms that the laptop cannot reach any DHCP server, as APIPA addresses are not routable and are only used for link-local communication. Therefore, the most likely cause is that the DHCP server is unreachable or not responding to the laptop's DHCP request.

Answer

The laptop's DNS server settings are incorrect.

Answer

The laptop has a static IP address configured that conflicts with another device.

Answer

The Ethernet cable is faulty or disconnected.

Question 10

A network engineer is troubleshooting a link between two Cisco Catalyst 9300 switches that are connected via a 10GBASE-SR SFP+ module on each end over OM3 multimode fiber. The link is up, but the interface counters show a high number of CRC errors and runts. The engineer runs 'show interfaces Gi1/0/1' and 'show interfaces Gi1/0/1 transceiver details'. What is the most likely cause of the errors?

Accepted Answer

The receive optical power is too low, indicating a fiber or connector issue.. The high CRC errors and runts on a 10GBASE-SR link over OM3 fiber, combined with the 'show interfaces transceiver details' command, point to a physical-layer issue. Low receive optical power (below the receiver sensitivity threshold) causes bit errors that manifest as CRC errors and runts, even though the link is up. This is the most common cause when the fiber and transceivers are otherwise compatible.

Answer

The SFP+ module is faulty and needs replacement.

Answer

The fiber patch cables are too long, exceeding the 300-meter distance limit for 10GBASE-SR over OM3 fiber.

Answer

The interface speed is mismatched; the switch interface shows 1000Mb/s but the SFP+ is 10GBASE-SR.

Question 11

A network technician is troubleshooting a newly installed fiber link between two Cisco Catalyst 9300 switches. The link is up, but the interface shows excessive CRC errors and input errors. The technician runs 'show interfaces' and 'show interfaces transceiver details' on the suspect interface. Based on the output, what is the most likely cause of the errors?

Accepted Answer

The receive power is too low, likely due to a dirty or damaged fiber connector or excessive attenuation.. The output from 'show interfaces transceiver details' would show the receive power level. A receive power that is too low (e.g., below the receiver sensitivity threshold) indicates excessive signal loss, often due to dirty or damaged fiber connectors, poor splices, or excessive cable attenuation. This causes bit errors that manifest as CRC and input errors, even though the link is physically up. Option D correctly identifies this as the most likely cause.

Answer

The interface is configured for full duplex but the switchport is set to auto-negotiation, causing a duplex mismatch.

Answer

The SFP transceiver is faulty because the transmit power is too low at -3.5 dBm.

Answer

The fiber cable is too long for the SX SFP, exceeding the distance limit.

Question 12

A network engineer is troubleshooting a link between two Cisco Catalyst 9300 switches that are connected via a single-mode fiber optic cable. The link is up, but the interface counters show a high number of CRC errors and frame check sequence (FCS) errors. The interface is configured for 1000 Mbps and full duplex on both ends. What is the most likely cause of these errors?

Accepted Answer

Faulty or dirty fiber optic cable or connectors. CRC and FCS errors indicate corruption at the data-link layer, typically caused by physical-layer issues such as signal degradation. Since the link is up and both ends are configured for 1000 Mbps full duplex, a speed/duplex mismatch is ruled out. Dirty or faulty single-mode fiber connectors or the cable itself can introduce optical signal loss or reflections, leading to bit errors that manifest as CRC/FCS errors.

Answer

A speed or duplex mismatch between the two switches

Answer

Incorrect SFP+ module type inserted in the switch

Answer

Excessive cable length beyond the distance limit

Question 13

Which TWO statements about fiber optic cables and SFP/SFP+ transceivers are correct?

Accepted Answer

Single-mode fiber (SMF) uses a smaller core diameter than multimode fiber (MMF).. Single-mode fiber (SMF) has a core diameter of about 9 microns, which is smaller than multimode fiber (MMF) cores of 50 or 62.5 microns. Option C is correct because SFP+ transceivers are indeed designed for 10 Gigabit Ethernet, supporting data rates up to 10 Gbps. Option B is wrong because multimode fiber is used for shorter distances (up to a few hundred meters) due to higher modal dispersion, while single-mode fiber supports longer distances (tens of kilometers). Option D is wrong because standard SFP modules support up to 1 Gbps, not 10 Gbps; SFP+ modules handle 10 Gbps. Option E is wrong because a 9-micron core is characteristic of single-mode fiber, not multimode fiber.

Answer

Multimode fiber supports longer distances than single-mode fiber.

Answer

SFP modules support data rates up to 10 Gbps.

Answer

Multimode fiber typically has a core diameter of 9 microns.

Question 14

Which TWO statements about fiber optic cable types and SFP transceivers are correct?

Accepted Answer

Multimode fiber is commonly used in campus and data center environments for distances up to several hundred meters.. Multimode fiber (MMF) has a larger core (typically 50/125 µm or 62.5/125 µm) and is used for short-reach, cost-effective connections up to a few hundred meters, making option B correct. Single-mode fiber (SMF) uses a much smaller core (~9 µm) and laser-based optics to achieve distances of 10 km or more, so option D is correct. Option A is wrong because it reverses the core size characteristic: SMF has a smaller core, and the given dimensions (62.5/125 µm) refer to multimode. Option C is wrong because SFP+ is a 10 Gbps form factor and is not inherently backward compatible with 1 Gbps SFP modules unless the switch port explicitly supports dual-rate operation. Option E is incorrect because fiber optic cables are inherently immune to electromagnetic interference (EMI) and therefore never require EMI shielding in any environment; the false statement claims they need shielding.

Answer

Single-mode fiber uses a larger core (typically 62.5/125 µm) and supports longer distances than multimode fiber.

Answer

SFP+ transceivers support data rates up to 1 Gbps and are backward compatible with standard SFP modules.

Answer

Fiber optic cables must be run with EMI shielding when deployed in environments with high electromagnetic interference.

Question 15

Drag and drop the cable/transceiver types on the left to the correct descriptions on the right.

Accepted Answer

Cat5e: Ethernet cable supporting up to 1 Gbps at 100 MHz. Cat5e supports up to 1 Gbps at 100 MHz, standard for 1000BASE-T over 100 meters. Cat6 supports up to 10 Gbps at 250 MHz but is limited to 55 meters for 10GBASE-T. Cat6a supports 10 Gbps at 500 MHz over full 100 meters. Single-mode fiber uses laser light for long distances, typically beyond 1 km.