CCNA Network Infrastructure and Connectivity Practice Test 21 — 15 Questions

Question 1

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

Accepted Answer

Client sends SYN (seq=x). The TCP three-way handshake begins with the client sending a SYN (A) to initiate the connection. The server replies with a SYN-ACK (B) to acknowledge the client's SYN and provide its own sequence number. Finally, the client sends an ACK (C) to confirm the server's SYN, completing the handshake. Option D, "Server sends ACK (ack=x+1)," is not part of the three-way handshake; an ACK from the server would be redundant at this stage and actually occurs during the four-way connection termination, not establishment.

Answer

Server sends ACK (ack=x+1)

Question 2

Which single OSI model layer is responsible for both end‑to‑end reliable data delivery and segmenting data into smaller units?

Accepted Answer

Transport layer (Layer 4). The Transport layer (Layer 4) is the only OSI layer responsible for both end‑to‑end reliable data delivery (via protocols like TCP) and segmenting data into smaller units (segments). The Network layer (Layer 3) handles routing and packetizing but does not provide reliability. Therefore, only the Transport layer fulfills both requirements.

Answer

Data Link layer (Layer 2)

Answer

Network layer (Layer 3)

Answer

Session layer (Layer 5)

Answer

Transport layer (Layer 4) and Network layer (Layer 3)

Question 3

Drag and drop the following steps into the correct order to isolate CRC errors, duplex mismatches, and flapping on a Cisco IOS-XE interface.

Accepted Answer

Enter configuration mode, enable debugs, monitor logs, analyze data, apply fixes and verify.. First enter configuration mode, then enable debugs to capture errors, monitor logs, analyze the data, and finally apply fixes and verify.

Answer

Enable debugs, enter configuration mode, monitor logs, analyze data, apply fixes and verify.

Answer

Monitor logs, enter configuration mode, enable debugs, analyze data, apply fixes and verify.

Answer

Enter configuration mode, monitor logs, enable debugs, analyze data, apply fixes and verify.

Question 4

Which of the following shows the correct order of steps to troubleshoot a suspected duplex mismatch and CRC errors on a Cisco IOS-XE interface?

Accepted Answer

Enter global configuration mode, then interface configuration mode for the affected interface, set duplex to full and speed to match the connected device, exit configuration mode, and verify the interface status.. The proper troubleshooting flow requires moving through the correct configuration hierarchy: from privileged EXEC mode you first enter global configuration mode. Then you specify the affected interface to enter interface configuration mode, where the duplex and speed settings are applied. After making the changes, you exit all configuration modes back to privileged EXEC and use show commands to verify the interface status. Option A follows this exact sequence. Option B is wrong because it tries to enter interface configuration without global config. Option C mistakenly attempts to set duplex/speed globally, which is not allowed. Option D not only omits global config but also exits to the wrong mode, leaving you in global configuration instead of privileged EXEC for verification.

Answer

Enter interface configuration mode directly, set duplex and speed, then exit to privileged EXEC mode and verify the interface status.

Answer

Enter global configuration mode, set duplex and speed globally, then exit and verify the interface status.

Answer

Enter interface configuration mode, set duplex and speed, then exit to global configuration mode and verify the interface status.

Question 5

Drag and drop the following steps into the correct order to isolate and resolve interface CRC errors, duplex mismatches, and flapping on a Cisco IOS-XE switch.

Accepted Answer

Check interface statistics for CRC errors, runts, or giants; verify duplex and speed settings; replace faulty cables or transceivers; monitor interface to confirm resolution.. Start with checking statistics to identify issues, then verify duplex and cable, replace hardware if needed, and finally confirm resolution.

Answer

Replace the cable immediately; then check interface statistics; if errors persist, adjust duplex settings; finally, monitor the interface.

Answer

Verify duplex and speed settings; then replace the cable; check interface statistics; finally, monitor the interface.

Answer

Monitor the interface for errors; then replace the cable; if errors continue, adjust duplex settings; finally, check interface statistics.

Question 6

Drag and drop the following troubleshooting steps into the correct order to isolate CRC errors, duplex mismatches, and flapping on a Cisco IOS-XE interface.

Accepted Answer

Use show commands to gather interface statistics and identify errors.. The correct troubleshooting order is: first, use show commands to gather interface statistics and identify CRC errors, duplex mismatches, and flapping (Step A). Next, apply configuration changes to resolve the identified issues (Step C). Then, clear interface counters to reset the statistics (Step B). Finally, verify the fix by monitoring interface statistics after clearing counters (Step D). This order ensures that after applying changes, you clear the old error data so that verification shows only new errors, confirming the fix. Clearing counters before verification provides a clean baseline.

Question 7

Drag and drop the following steps into the correct order to troubleshoot a suspected duplex mismatch and CRC errors on a Cisco switch interface using CLI commands.

Accepted Answer

1. Use 'show interfaces' to check for CRC errors and duplex mismatch. 2. Manually set speed and duplex on both ends to match. 3. Use 'clear counters' to reset interface statistics. 4. Use 'show interfaces' again to verify no new errors.. Start by examining current interface stats, then fix the mismatch, and finally clear and recheck counters.

Answer

1. Use 'clear counters' to reset interface statistics. 2. Use 'show interfaces' to check for CRC errors. 3. Manually set speed and duplex on both ends to match. 4. Use 'show interfaces' again to verify no new errors.

Answer

1. Use 'show interfaces' to check for CRC errors. 2. Use 'clear counters' to reset interface statistics. 3. Manually set speed and duplex on both ends to match. 4. Use 'show interfaces' again to verify no new errors.

Answer

1. Manually set speed and duplex on both ends to match. 2. Use 'show interfaces' to check for CRC errors. 3. Use 'clear counters' to reset interface statistics. 4. Use 'show interfaces' again to verify no new errors.

Question 8

Which TWO interface error counters indicate a Layer 1 issue?

Accepted Answer

CRC errors. CRC errors occur when the cyclic redundancy check computed at the receiver does not match the value appended by the sender, indicating that the frame was corrupted during transmission. This corruption is typically caused by physical-layer problems such as faulty cabling, bad connectors, or excessive electrical noise. Runts are frames that are smaller than the minimum Ethernet frame size of 64 bytes (excluding preamble), and they often result from collisions or transceiver issues that are Layer 1 phenomena. Both counters directly point to physical-layer impairments rather than logical or congestion-related issues.

Answer

Output queue drops

Answer

Input errors

Answer

Ignored packets

Question 9

Which TWO of the following are essential IPv4 host parameters that must be correctly configured for a host to communicate with devices on remote networks?

Accepted Answer

Default gateway. The default gateway is the IP address of the router interface on the local subnet; when a host needs to communicate with a device on a remote network, it must forward packets to the default gateway because the destination is not reachable locally. The subnet mask is equally essential because the host uses it (along with its own IP address) to determine whether a destination IP address is on the same local network or a remote network; without a correctly configured subnet mask, the host cannot make this determination and may misroute traffic. DNS server address is only for name resolution and is not required for IP-level connectivity, MAC address is a Layer 2 address already present on the NIC, and hostname is a local identifier irrelevant to routing.

Answer

DNS server address

Answer

MAC address

Answer

Host name

Question 10

Drag and drop the following steps into the correct order to configure a WLAN for WPA3-Enterprise on a Cisco WLC and sequence a wireless client association process.

Accepted Answer

Create WLAN with WPA3-Enterprise security, enable WLAN, client associates, 802.1X authentication, DHCP IP assignment. The configuration creates the WLAN with WPA3-Enterprise security, enables it, then the client associates and completes 802.1X authentication before getting an IP.

Answer

Create WLAN with WPA3-Enterprise security, enable WLAN, client associates, DHCP IP assignment, 802.1X authentication

Answer

Enable WLAN, create WLAN with WPA3-Enterprise security, client associates, 802.1X authentication, DHCP IP assignment

Answer

Create WLAN with WPA3-Enterprise security, client associates, enable WLAN, 802.1X authentication, DHCP IP assignment

Question 11

Drag and drop the following steps into the correct order to configure a WPA3 SSID on a Cisco WLC and complete a wireless client association.

Accepted Answer

Create a new WLAN with SSID and WPA3-Personal security, enable the WLAN, then the client scans, associates, and obtains an IP via DHCP.. The steps follow the standard WLC configuration sequence: create the WLAN, set WPA3-Personal security, enable it, then the client associates and gets an IP.

Answer

Enable the WLAN first, then create the WLAN with SSID and WPA3-Personal security, then the client associates and obtains an IP.

Answer

Create the WLAN, enable it, then configure WPA3-Personal security, then the client associates and gets an IP.

Answer

Create the WLAN, configure WPA3-Personal security, enable the WLAN, then the client obtains an IP before associating.

Question 12

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

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

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

Accepted Answer

Enter global configuration mode, create WLAN profile, configure WPA3-Personal (SAE) security, enable WLAN, client associates, client obtains IP via DHCP.. The configuration order follows the Cisco IOS-XE WLC CLI: first enter global config, create the WLAN profile, set security (WPA3-Personal/SAE), enable the WLAN, then the client associates and gets an IP via DHCP.

Answer

Enter global configuration mode, create WLAN profile, enable WLAN, configure WPA3-Personal (SAE) security, client associates, client obtains IP via DHCP.

Answer

Enter global configuration mode, configure WPA3-Personal (SAE) security, create WLAN profile, enable WLAN, client associates, client obtains IP via DHCP.

Answer

Enter global configuration mode, create WLAN profile, configure WPA3-Personal (SAE) security, enable WLAN, client obtains IP via DHCP, client associates.

Question 13

Which TWO statements correctly compare 802.11ac and 802.11ax features?

Accepted Answer

802.11ax uses OFDMA, while 802.11ac uses OFDM.. 802.11ax (Wi‑Fi 6) introduces Orthogonal Frequency Division Multiple Access (OFDMA), which allows multiple users to share subcarriers simultaneously, improving efficiency in dense environments. In contrast, 802.11ac (Wi‑Fi 5) uses Orthogonal Frequency Division Multiplexing (OFDM), where each transmission occupies the entire channel for a single user, leading to less efficient channel utilization. Option C is correct: WPA3 is mandatory for Wi‑Fi 6 (802.11ax) certification, while for 802.11ac it is optional—devices can still obtain Wi‑Fi 5 certification with WPA2 only. Option B is incorrect because 802.11ac supports a maximum of 256‑QAM; 1024‑QAM is first introduced with 802.11ax. Option D is wrong: 802.11ac operates exclusively in the 5 GHz band, but 802.11ax operates in both 2.4 GHz and 5 GHz. Option E is false: both standards support 20, 40, 80, and 160 MHz channel widths; 802.11ac does not exclusively use 80 MHz, and 802.11ax does not use 160 MHz exclusively.

Answer

Both 802.11ac and 802.11ax support 1024-QAM modulation.

Answer

Both standards use only the 5 GHz band.

Answer

802.11ac uses 80 MHz channels, while 802.11ax uses 160 MHz channels exclusively.

Question 14

Drag and drop the 802.11 standards on the left to their correct frequency band and maximum throughput on the right.

Accepted Answer

802.11b: 2.4 GHz, 11 Mbps. Each 802.11 standard operates in specific frequency bands and has a maximum theoretical throughput. 802.11a uses 5 GHz at 54 Mbps, 802.11b uses 2.4 GHz at 11 Mbps, 802.11g uses 2.4 GHz at 54 Mbps, 802.11n uses both 2.4 and 5 GHz up to 600 Mbps, 802.11ac uses 5 GHz up to 6.9 Gbps, and 802.11ax uses 2.4, 5, and 6 GHz up to 9.6 Gbps.

Question 15

Drag and drop the following troubleshooting steps into the correct order to diagnose a client connectivity issue using the OSI bottom-up method.

Accepted Answer

Check physical connectivity, then data link, then network, then transport, then application. The OSI bottom-up method starts at physical layer and moves up. This ensures that lower-layer issues are resolved before higher-layer troubleshooting, preventing wasted effort on symptoms caused by underlying problems.

Answer

Check application, then transport, then network, then data link, then physical

Answer

Check network, then data link, then physical, then transport, then application

Answer

Check physical, then network, then data link, then transport, then application