CCNA Network Infrastructure and Connectivity Practice Test 25 — 15 Questions

Question 1

You are connected via the console to R1, a new Cisco ISR 4321 router. The network team requires that all routers be reachable via SSH for management. R1's management interface is GigabitEthernet0/0 with IP 192.168.1.1/24. You need to configure SSH on R1, including a hostname, domain name, RSA key pair of 1024 bits, local user 'admin' with secret 'cisco123', and enable SSH version 2. Additionally, configure the vty lines to accept only SSH connections and use local authentication.

Accepted Answer

R1(config)# hostname R1
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa modulus 1024
R1(config)# username admin secret cisco123
R1(config)# ip ssh version 2
R1(config)# line vty 0 4
R1(config-line)# transport input ssh
R1(config-line)# login local. SSH configuration requires a hostname, domain name, RSA key pair, local username, and vty line settings. The command sequence ensures SSH version 2 is used and only SSH connections are accepted on the vty lines.

Answer

R1(config)# hostname R1
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa general-keys modulus 1024
R1(config)# username admin password cisco123
R1(config)# ip ssh version 2
R1(config)# line vty 0 4
R1(config-line)# transport input ssh telnet
R1(config-line)# login local

Answer

R1(config)# hostname R1
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa modulus 1024
R1(config)# username admin secret cisco123
R1(config)# ip ssh version 2
R1(config)# line vty 0 4
R1(config-line)# transport input all
R1(config-line)# login local

Answer

R1(config)# hostname R1
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa modulus 1024
R1(config)# username admin secret cisco123
R1(config)# ip ssh version 2
R1(config)# line vty 0 4
R1(config-line)# transport input ssh
R1(config-line)# password cisco123
R1(config-line)# login

Question 2

Which three of the following are characteristics of Layer 2 Ethernet switches that improve network performance? (Choose three.)

Accepted Answer

They create separate collision domains per port.. Layer 2 Ethernet switches improve network performance by creating separate collision domains per port, eliminating collisions between devices on different ports. They forward frames based on the destination MAC address, enabling efficient hardware-based switching. Cut-through switching reduces latency by starting to forward as soon as the destination MAC address is read. The other options are incorrect: switches do not reduce broadcast domains (broadcasts are forwarded to all ports in the same VLAN unless a router or VLAN segmentation is used); switches operate at Layer 2 using MAC addresses, not IP addresses; and unknown unicast frames are flooded out all ports except the incoming port, not automatically blocked, to ensure connectivity if the destination is unknown.

Answer

They reduce the number of broadcast domains.

Answer

They automatically block all unknown unicast frames.

Answer

They use IP addresses to make forwarding decisions.

Question 3

Which three statements about the Spanning Tree Protocol (STP) are true? (Choose three.)

Accepted Answer

STP uses Bridge Protocol Data Units (BPDUs) to exchange topology information.. All three statements are correct because STP relies on Bridge Protocol Data Units (BPDUs) to share topology information between switches, elects a root bridge by comparing bridge IDs (a combination of priority and MAC address, with the lowest value winning), and prevents loops by placing redundant ports into a blocking state (discarding state in Rapid PVST+). These are fundamental behaviors of the 802.1D Spanning Tree Protocol.

Answer

STP converges instantly after a topology change.

Answer

STP is used to increase the number of broadcast domains.

Answer

STP always uses the highest port cost to select the root port.

Question 4

Which three of the following are characteristics of wireless LAN (WLAN) operation in the 2.4 GHz and 5 GHz bands? (Choose three.)

Accepted Answer

Both bands can be used simultaneously by dual-band access points.. The 5 GHz band offers more non-overlapping channels (up to 23 or 25, depending on regulatory domain) compared to the 2.4 GHz band, which has only three non-overlapping channels (1, 6, 11). The 2.4 GHz band generally provides longer range due to better propagation characteristics and lower attenuation through obstacles. Dual-band access points can operate simultaneously on both bands, allowing clients to connect on either frequency.

Answer

Both bands require a license for operation in enterprise environments.

Answer

The 5 GHz band experiences more interference from Bluetooth devices.

Answer

The 2.4 GHz band supports higher data rates than the 5 GHz band.

Question 5

Which three of the following are characteristics of Layer 2 Ethernet switches that support VLANs? (Choose three.)

Accepted Answer

They forward frames based on the destination MAC address.. Layer 2 Ethernet switches that support VLANs forward frames based on the destination MAC address, which is the fundamental switching decision. They can segment a LAN into multiple broadcast domains because each VLAN creates its own isolated broadcast domain, preventing unnecessary traffic propagation. They use the Spanning Tree Protocol (STP) to prevent Layer 2 loops by dynamically blocking redundant paths, ensuring a loop-free topology.

Answer

They use ARP to resolve IP addresses to MAC addresses.

Answer

They perform routing between VLANs without a router.

Answer

They forward frames based on the destination IP address.

Question 6

Which three options correctly describe how a router processes a packet destined for a remote network? (Choose three.)

Accepted Answer

It decrements the Time-to-Live (TTL) field in the IP header.. When a router forwards a packet to a remote network, it first decrements the Time-to-Live (TTL) field in the IP header to prevent infinite loops. It then performs a routing table lookup for the destination IP address to determine the next-hop interface and IP. Finally, it rewrites the source and destination MAC addresses for the next hop, because MAC addresses are only relevant on the local link and must be updated at each Layer 3 hop.

Answer

It sends an ARP request for every destination IP address in the packet.

Answer

It encapsulates the entire packet in a new Layer 2 frame with the original MAC addresses.

Answer

It replaces the source IP address with its own outgoing interface IP.

Question 7

Which three statements are true about the operation of Dynamic Host Configuration Protocol (DHCP) in an enterprise network? (Choose three.)

Accepted Answer

A DHCP server uses the client's MAC address to uniquely identify and assign an IP address.. The DHCP client sends a DHCPDISCOVER message as a broadcast (destination IP 255.255.255.255) because it does not yet know the IP address of any DHCP server. The server uses the client's MAC address (from the CHADDR field) to uniquely identify the client and assign an IP address. DHCP options like default gateway and DNS server are carried in the DHCPOFFER and DHCPACK messages as part of the Options field, allowing the server to provide essential network configuration parameters.

Answer

The DHCPREQUEST message is always sent as a unicast directly to the DHCP server.

Answer

DHCP ensures that IP addresses are permanently assigned and never expire.

Answer

A DHCP relay agent is required only if the client and server are on the same subnet.

Question 8

Which three statements about Power over Ethernet (PoE) and PoE+ standards are correct? (Choose three.)

Accepted Answer

Powered devices (PDs) can negotiate power requirements using Link Layer Discovery Protocol (LLDP) with PoE extensions.. Option 1 is correct because the IEEE 802.3af PoE standard specifies a maximum power delivery of 15.4 watts per port at the PSE (Power Sourcing Equipment), with a minimum of 12.95 watts guaranteed at the PD (Powered Device) after cable losses. Option 2 is correct because the IEEE 802.3at PoE+ standard increases the maximum power per port to 30 watts at the PSE, with 25.5 watts available at the PD. Option 4 is correct because PDs can negotiate power requirements using LLDP with the IEEE 802.1AB LLDP-MED (Media Endpoint Discovery) extensions, which include PoE TLV (Type-Length-Value) fields for power negotiation beyond the simple classification method. Option 3 (both PoE and PoE+ use the same four pairs) is incorrect because both standards deliver power over only two pairs (spare or data pairs depending on mode); four-pair power delivery is introduced in IEEE 802.3bt (PoE++). Option 5 (PoE+ requires Category 3 cabling) is incorrect because PoE+ requires at least Category 5e cabling to support the higher power levels without excessive heat or signal degradation. Option 6 (PoE automatically disables power if a non-PoE device is detected) is incorrect because the PSE first performs a detection phase to identify a valid PoE signature; if none is found, power is never applied—so it is not disabled after being enabled.

Answer

Both PoE and PoE+ use the same four pairs of a twisted-pair cable for power delivery.

Answer

PoE+ requires Category 3 cabling or better.

Answer

PoE automatically disables power if a non-PoE device is detected.

Question 9

Which three of the following are correct steps in the process of CDP (Cisco Discovery Protocol) neighbor discovery? (Choose three.)

Accepted Answer

CDP is enabled by default on Cisco devices and runs over all interfaces that support SNAP headers.. CDP is a Cisco proprietary Layer 2 protocol that uses multicast MAC address 01:00:0C:CC:CC:CC to send advertisements to directly connected neighbors. Advertisements include device identifier, platform, and capabilities. CDP is enabled by default on Cisco devices and runs over interfaces supporting SNAP headers. Incorrect options: CDP advertisements are sent every 60 seconds by default (not 30); CDP discovers only directly connected neighbors (not devices more than one L2 hop away); CDP does not require both devices to be in the same IP subnet because it operates at Layer 2.

Answer

CDP advertisements are sent every 30 seconds by default.

Answer

CDP requires that both devices be in the same IP subnet.

Answer

CDP can discover devices that are more than one Layer 2 hop away.

Question 10

Drag and drop the following steps into the correct order to describe the data encapsulation process as it flows down the OSI model from the source host.

Accepted Answer

Application data is generated and passed to the Transport layer.. Encapsulation proceeds from the top OSI layers to the bottom. First, the application generates data (Step 1). The Transport layer then adds a header (TCP or UDP) to create a segment (Step 2) because this is the first step in preparing data for reliable delivery. The Network layer adds an IP header to form a packet (Step 3), which provides logical addressing and routing information. The Data Link layer adds a frame header and trailer to create a frame (Step 4), enabling physical addressing (MAC) and error detection. Finally, the Physical layer converts the frame to bits for transmission (Step 5), as it is the layer that ultimately puts signals on the wire.

Question 11

Drag and drop the following steps into the correct order to configure a Windows 10 host with a static IPv4 address, subnet mask, and default gateway.

Accepted Answer

Open Control Panel and navigate to Network and Sharing Center.. The correct order begins with opening Network and Sharing Center to access network settings. Then, you must click 'Change adapter settings' to see the list of network connections. Right-clicking the appropriate adapter and selecting Properties opens its configuration. Selecting IPv4 and clicking Properties allows you to set the IP parameters. Choosing 'Use the following IP address' enables the fields for static input. Finally, entering the IP address, subnet mask, and default gateway followed by OK/Close applies the configuration. This sequence follows the logical navigation of the Windows GUI to reach the static IP assignment interface.

Question 12

Drag and drop the following steps into the correct order to diagnose and resolve a duplex/speed mismatch causing interface errors on a Cisco switch.

Accepted Answer

Enter the 'show interfaces' command to examine interface status and error counters.. The correct diagnostic process begins by collecting interface statistics with 'show interfaces' to detect anomalies (step 1). If CRC errors, runts, and late collisions are present, these indicate a duplex mismatch (step 2). Next, check the current duplex and speed configuration for that interface using 'show interfaces <int>' (step 3). Compare this setting with the expected configuration or with the remote device's interface (step 4) to confirm the mismatch. Based on the findings, apply the correct duplex and speed commands to align both ends (step 5). Finally, verify that the error counters stop incrementing after the fix (step 6).

Question 13

Drag and drop the following steps into the correct order to troubleshoot a Windows client that is unable to reach a remote server.

Accepted Answer

Run ipconfig /all to check IP configuration, subnet mask, default gateway, and DNS servers.. The correct troubleshooting order starts with verifying the client's IP configuration using ipconfig /all (A) to ensure the device has proper addressing. Next, test the TCP/IP stack by pinging the loopback address 127.0.0.1 (B). Then, ping the client's own IP address (C) to confirm the network interface card is operational. After that, ping the default gateway (D) to verify local network connectivity. If successful, ping the remote server (E) to test end-to-end connectivity. If that fails, use tracert (F) to identify where the path breaks. This bottom-up approach isolates the problem starting from the local host outwards.

Question 14

Drag and drop the following steps into the correct order to describe how data is encapsulated as it travels down the OSI model layers.

Accepted Answer

Application data is generated by the upper layers.. Data originates at the application layer as user data. The transport layer then encapsulates this data by adding a header (e.g., TCP or UDP) to create a segment. The network layer further adds an IP header to the segment, forming a packet. Next, the data link layer appends a frame header and trailer to the packet, resulting in a frame. Finally, the physical layer converts the entire frame into bits for electrical, optical, or radio transmission. This sequence follows the standard top-down encapsulation process in network communication.

Question 15

Drag and drop the following steps into the correct order to troubleshoot a link-down issue on a GigabitEthernet interface using an SFP transceiver.

Accepted Answer

Identify the interface with the link-down condition using the 'show interfaces' command and note any input/output errors.. Troubleshooting begins by verifying the interface status and physical layer (steps 1-2). Next, you ensure the SFP is physically and logically recognized (step 3) before retrieving specific diagnostic data (step 4). Only after confirming the health of the transceiver do you take corrective action (step 5), because replacing hardware without diagnostics may waste resources.