CCNA Network Infrastructure and Connectivity Practice Test 20 — 15 Questions

Question 1

A network administrator is troubleshooting a Windows 10 workstation that cannot access the internet. The workstation receives an IPv4 address starting with 169.254.x.x. The network uses DHCP, and other workstations on the same subnet are working correctly. What is the most likely cause of this issue?

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

Accepted Answer

The workstation's network cable is unplugged or faulty, preventing DHCP communication.. The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address assigned by Windows when DHCP fails. Since other workstations on the same subnet work correctly, the DHCP server and network are functional, isolating the issue to the specific workstation. A faulty or unplugged network cable would prevent the workstation from sending DHCP Discover messages, causing it to fall back to APIPA.

Answer

The workstation's DNS server settings are incorrect.

Answer

The DHCP server has exhausted its address pool.

Answer

The workstation's default gateway is misconfigured.

Question 2

A network administrator is configuring a new Windows 10 workstation on a network that uses DHCP. The workstation receives an IPv4 address of 169.254.10.20 with a subnet mask of 255.255.0.0 and no default gateway. The user cannot access the internet or other subnets. What is the most likely cause of this issue?

Accepted Answer

The DHCP server is unreachable or not responding.. The IP address 169.254.10.20 with a /16 subnet mask is an Automatic Private IP Addressing (APIPA) address, which Windows assigns when a DHCP discovery broadcast (DHCPDISCOVER) fails to receive a response from a DHCP server. Without a valid DHCP lease, the workstation has no default gateway, so it cannot communicate outside its local subnet, explaining the lack of internet or inter-subnet access. The most likely cause is that the DHCP server is unreachable or not responding, forcing the client to self-assign an APIPA address.

Answer

The workstation has a duplicate IP address conflict.

Answer

The workstation's DNS server configuration is incorrect.

Answer

The workstation's subnet mask is misconfigured.

Question 3

A network engineer is troubleshooting a wireless performance issue in a dense office environment. Clients on the 5 GHz band are experiencing low throughput even though they are close to the AP. The AP is a Cisco 9130AXI running IOS-XE 17.9. What is the most likely cause of the poor performance?

Accepted Answer

The AP is operating in 802.11ac mode instead of 802.11ax, and the 80 MHz channel bonding is causing high interference in the dense environment.. In a dense office environment, using 80 MHz channel bonding with 802.11ac (Wave 2) increases the likelihood of co-channel interference and overlapping basic service sets (OBSS), which degrades throughput despite strong signal. The Cisco 9130AXI supports 802.11ax (Wi-Fi 6), which includes OFDMA and better spatial reuse, but if the AP is configured for 802.11ac mode, it loses these efficiency gains and suffers from the wide channel's interference penalty.

Answer

The AP is using an incorrect channel width of 80 MHz, which is not supported by 802.11ac.

Answer

The AP has DFS non-compliance, which prevents it from using channel 36 and causes the radio to operate at reduced power.

Answer

The AP is using WPA2-PSK instead of WPA3, which causes lower throughput due to weaker encryption.

Question 4

Which TWO statements correctly describe differences between 802.11ac (Wi-Fi 5) and 802.11ax (Wi-Fi 6)?

Accepted Answer

802.11ax supports 1024-QAM modulation, whereas 802.11ac supports up to 256-QAM.. Options B and D are correct. 802.11ax (Wi-Fi 6) introduces 1024-QAM for higher data rates (B), while 802.11ac maxes at 256-QAM. Additionally, 802.11ax supports both 2.4 GHz and 5 GHz bands, whereas 802.11ac is limited to 5 GHz only (D). Option A is incorrect because it reverses the roles: 802.11ac uses OFDM, and 802.11ax uses OFDMA. Option C is incorrect because 802.11ax also operates in 2.4 GHz. Option E is incorrect because Target Wake Time (TWT) is introduced in 802.11ax, not 802.11ac.

Answer

802.11ac uses OFDMA, while 802.11ax uses only OFDM.

Answer

Both 802.11ac and 802.11ax operate exclusively in the 5 GHz band.

Answer

802.11ac introduces target wake time (TWT) for improved power saving, but 802.11ax does not support it.

Question 5

Drag and drop the wireless terms on the left to the correct descriptions on the right.

Options:
A: SSID: The network name broadcast by an access point to identify the wireless network.
B: BSSID: The MAC address of the access point's radio interface, used to uniquely identify a BSS.
C: RSSI: A measurement of the power level of the received radio signal, indicating signal strength.
D: DFS: A mechanism that allows wireless devices to avoid interference with radar systems by dynamically selecting channels.

Accepted Answer

SSID: The network name broadcast by an access point to identify the wireless network.. SSID (Service Set Identifier) is the network name broadcast by an access point to identify the wireless network, allowing clients to distinguish between different networks. BSSID (Basic Service Set Identifier) is the MAC address of the AP's radio interface, uniquely identifying a specific BSS. RSSI (Received Signal Strength Indicator) measures the power level of the received radio signal, indicating signal strength. DFS (Dynamic Frequency Selection) is a mechanism that allows wireless devices to avoid interference with radar systems by dynamically selecting channels. Each term correctly matches the provided description.

Question 6

A network technician is troubleshooting a connectivity issue for a PC connected to switch port Gi1/0/12. The PC can ping its default gateway (192.168.10.1) but cannot ping a server at 192.168.20.10. The switch is configured with VLAN 10 for the access port and is connected to a router-on-a-stick. The technician runs 'show vlan brief' and 'show interfaces trunk' on the switch. What is the most likely cause of the problem?

Accepted Answer

The router is missing a subinterface for VLAN 20.. The PC can ping its default gateway (192.168.10.1) but not the server at 192.168.20.10, indicating Layer 3 routing is failing between VLANs. Since the switch is configured with VLAN 10 for the access port and uses a router-on-a-stick, the router must have a subinterface for VLAN 20 to route traffic to the server's subnet. The absence of a subinterface for VLAN 20 prevents the router from forwarding packets from VLAN 10 to VLAN 20, making option B correct.

Answer

The trunk port Gi1/0/24 is not in trunking mode.

Answer

The switch port Gi1/0/12 is not assigned to VLAN 10.

Answer

The PC has a duplicate IP address with the server.

Question 7

Which TWO commands would a network administrator use to verify that a client has received a valid IP address from a DHCP server and can resolve domain names to IP addresses?

Accepted Answer

ipconfig /all. (ipconfig /all) is correct because it displays the full TCP/IP configuration for all network adapters, including whether DHCP is enabled, the assigned IP address, subnet mask, default gateway, and the DHCP server address. This allows the administrator to confirm that the client received a valid IP address from the DHCP server. Option D (nslookup www.courseiva.com) is correct because it queries the configured DNS server to resolve the domain name to an IP address, verifying that name resolution is working. Option B (ping 127.0.0.1) only tests the local TCP/IP stack and does not verify DHCP assignment or DNS resolution. Option C (tracert 8.8.8.8) uses an IP address directly and does not test domain-name resolution. Option E (arp -a) displays the ARP cache, which is unrelated to DHCP or DNS.

Answer

ping 127.0.0.1

Answer

tracert 8.8.8.8

Answer

arp -a

Question 8

Which TWO commands would a network engineer use to verify that a Windows client has received an IP address from a DHCP server and can resolve a domain name to an IP address?

Accepted Answer

ipconfig /all. `ipconfig /all` displays the full TCP/IP configuration for all adapters, including whether the IP address was obtained from a DHCP server (the DHCP Enabled and DHCP Server fields). Option D is correct because `nslookup www.courseiva.com` queries the configured DNS server to resolve the domain name to an IP address, confirming DNS resolution works.

Answer

ping 8.8.8.8

Answer

tracert www.courseiva.com

Answer

arp -a

Question 9

Which command or tool would a network engineer use to verify if a client has a duplicate IP address conflict on the local subnet?

Accepted Answer

arp -a. The two tools to verify a duplicate IP conflict are arp -a and ping. The arp -a command displays the ARP cache; if a duplicate IP exists, the ARP table may show multiple MAC addresses for the same IP or rapid changes. Ping can be used to send traffic to the local IP address; if a reply is received from a different MAC address than expected, it indicates a conflict. Together, these commands help network engineers confirm IP address duplication. Other commands like ipconfig /all, nslookup, and tracert do not directly reveal such conflicts.

Answer

ipconfig /all

Answer

nslookup

Answer

tracert

Question 10

A network administrator is troubleshooting a Windows 10 workstation that cannot access the internet. The workstation receives an IPv4 address starting with 169.254.x.x. The network uses DHCP, and other workstations on the same subnet are working correctly. What is the most likely cause of this issue?

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

Accepted Answer

The workstation is unable to communicate with a DHCP server due to a faulty network cable.. The IP address 169.254.10.55 falls within the Automatic Private IP Addressing (APIPA) range (169.254.0.0/16, RFC 3927). This address is assigned by the operating system when a DHCP client fails to receive a response from a DHCP server. A faulty network cable would prevent the workstation from communicating with the DHCP server, causing the client to self-assign an APIPA address after the DHCP discovery process times out.

Answer

The workstation has a duplicate IP address conflict with another device.

Answer

The workstation's DNS server settings are misconfigured.

Answer

The workstation is connected to the wrong VLAN, causing it to receive an incorrect IP address.

Question 11

A network administrator receives a call from a user who cannot access any external websites from their wired workstation. The user can ping the default gateway successfully, but fails to ping 8.8.8.8. The administrator runs ipconfig /all on the workstation and sees an IP address of 192.168.1.50, subnet mask 255.255.255.0, and default gateway 192.168.1.1. What is the most likely cause of this issue?

Accepted Answer

The workstation has an incorrect default gateway configured.. The user can successfully ping 192.168.1.1, proving local IP connectivity to that device. However, the device at 192.168.1.1 may not be the correct default gateway for reaching external networks; the actual gateway router might be at a different IP (e.g., 192.168.1.254). This misconfiguration explains why pings to 8.8.8.8 fail even though the local gateway responds, as the workstation sends external traffic to the wrong next-hop address.

Answer

The workstation has a duplicate IP address on the network.

Answer

The workstation is connected to the wrong VLAN.

Answer

The workstation has a DNS misconfiguration.

Question 12

Drag and drop the following steps into the correct order to install a new fiber optic cable and SFP module on a Cisco switch, then verify the interface status.

Accepted Answer

Insert the SFP module into the port while the switch is powered on. The correct procedure for installing a fiber optic cable and SFP module on a modern Cisco switch is: first, insert the SFP module into the port while the switch is powered on (hot-swap); second, connect the fiber optic cable to the SFP module; third, verify the interface status using 'show interfaces status'. Option D is incorrect because fiber optic cables cannot connect directly to a switch port without an SFP module, and powering down the switch is unnecessary when hot-swapping SFPs.

Answer

Power down the switch, connect the fiber optic cable directly to the switch port without an SFP module, power up the switch, and verify the interface status.

Question 13

Which TWO statements accurately describe the characteristics and deployment considerations for fiber optic cabling in a modern enterprise network?

Accepted Answer

When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters.. The correct statements are that 10GBASE-SR over OM3 multimode fiber supports up to 300 meters and that fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for electrically noisy environments. Single-mode fiber actually has a smaller core diameter than multimode, making option A incorrect. Multimode fiber is designed for shorter links, so option B is wrong. Standard 1000BASE-LX SFP transceivers over single-mode fiber are limited to 5 km, not 10 km, so option C is inaccurate.

Answer

Single-mode fiber (SMF) typically uses a larger core diameter than multimode fiber (MMF).

Answer

Multimode fiber (MMF) is generally preferred for longer-distance links, such as between buildings on a campus network.

Answer

A 1000BASE-LX SFP transceiver operating over single-mode fiber can support distances up to 10 km.

Question 14

Drag and drop the following steps into the correct order to sequence the TCP three-way handshake between a client and a server.

Accepted Answer

Client sends SYN. The TCP three-way handshake starts with the client sending a SYN, followed by the server responding with SYN-ACK, and finally the client sending an ACK to establish the connection.

Answer

Server sends ACK

Question 15

Which of the following correctly describes the sequence of the TCP three-way handshake between a client and a server?

Accepted Answer

Client sends SYN, Server responds with SYN-ACK, Client sends ACK. The TCP three-way handshake establishes a reliable connection in three steps: the client sends a SYN, the server replies with SYN-ACK, and the client acknowledges with an ACK. Option A correctly depicts this. Option B omits the server's SYN, leaving synchronization incomplete. Option C reverses the roles by having the server initiate, which never occurs in a standard handshake. Option D begins with a SYN-ACK, which is not a valid initial packet; the handshake must start with a SYN.

Answer

Client sends SYN, Server responds with ACK, Client sends SYN-ACK

Answer

Server sends SYN, Client responds with SYN-ACK, Server sends ACK

Answer

Client sends SYN-ACK, Server responds with SYN, Client sends ACK