CCNA Network Infrastructure and Connectivity Practice Test 24 — 15 Questions

Question 1

You are connected to R1 via console. R1's GigabitEthernet0/1 interface connects to a remote site switch over a 2 km fiber link. The current configuration shows speed and duplex set to 1000 Mbps and full, but the interface is down/down due to an SFP mismatch. Review the exhibit, identify the problem, and correct it so that the interface comes up and communicates at the correct speed and duplex. Additionally, ensure the interface is configured to auto-negotiate properly for future cable replacements.

Accepted Answer

Replace the SFP with a 1000BASE-LX module, remove the manual speed and duplex settings, and issue the no shutdown command.. The interface was administratively shut down (shutdown command) and had hard-coded speed 1000 and duplex full, which is incompatible with the 2 km fiber link requiring a long-haul SFP (e.g., 1000BASE-LX). The correct fix is to remove the manual speed/duplex settings, enable auto-negotiation (which is default but overridden), and then no shutdown. For a 2 km link, a 1000BASE-LX SFP is required; the existing SFP (likely 1000BASE-SX, max 550 m) caused the link to be down. After replacing with the correct SFP, the interface should come up. Commands: interface Gi0/1, no speed, no duplex, no shutdown.

Answer

Replace the SFP with a 1000BASE-SX module, keep the manual speed 1000 and duplex full, and issue the no shutdown command.

Answer

Keep the existing SFP, change the speed to 100 and duplex to half, and issue the no shutdown command.

Answer

Replace the SFP with a 1000BASE-LX module, keep the manual speed 1000 and duplex full, and issue the no shutdown command.

Question 2

You are connected to R1 via the console. R1 and R2 are directly connected via their GigabitEthernet0/0 interfaces. The link between them is down. Your task is to diagnose and fix the issue: R1's interface is configured for 100 Mbps full-duplex, but R2 is using auto-negotiation. Additionally, the link requires a Gigabit Ethernet connection over a distance of 5 km. Configure R1's interface to match R2's settings (auto-negotiation) and then select and install the correct SFP module to support the 5 km distance requirement.

Accepted Answer

Configure R1 with 'no speed', 'no duplex', and 'negotiation auto' on GigabitEthernet0/0, then replace the SFP module with a 1000BASE-LX SFP.. The link is down because R1 is forcing speed 100 and full-duplex while R2 is using auto-negotiation. When one side is hard-coded and the other is set to auto, auto-negotiation fails and the link does not come up. The fix is to enable auto-negotiation on R1 by removing the manual speed and duplex settings with the 'no speed' and 'no duplex' commands, and then using 'negotiation auto'. For the 5 km distance, a standard 1000BASE-SX SFP (550 m) is insufficient; a 1000BASE-LX SFP (up to 10 km) is required. The candidate must also replace the SFP module with a compatible LX SFP.

Answer

Configure R1 with 'speed 1000' and 'duplex full' on GigabitEthernet0/0, then replace the SFP module with a 1000BASE-SX SFP.

Answer

Configure R1 with 'no speed', 'no duplex', and 'negotiation auto' on GigabitEthernet0/0, then replace the SFP module with a 1000BASE-SX SFP.

Answer

Configure R1 with 'speed 100' and 'duplex full' on GigabitEthernet0/0, then replace the SFP module with a 1000BASE-LX SFP.

Question 3

You are connected to R1 via the console. R1 and R2 are connected via a fiber link using SFPs. The link is not coming up. Configure the correct SFP type on R1's interface GigabitEthernet0/0 to support the required 2 km distance, and fix any auto-negotiation or speed/duplex misconfiguration so that the link becomes operational.

Accepted Answer

Replace SFP with 1000BASE-LX, configure 'no negotiation auto' on GigabitEthernet0/0, and remove 'speed 1000' and 'duplex full'.. For a 2 km fiber link, a 1000BASE-LX SFP is required (supports up to 10 km). Fiber SFPs like 1000BASE-LX typically do not support auto-negotiation; speed and duplex are fixed. Therefore, the interface should have 'no negotiation auto' configured and no explicit speed/duplex commands. Option A implements these changes. Option B uses 1000BASE-SX, which is suitable only for up to 550 m. Option C leaves auto-negotiation enabled, which is unsupported. Option D sets speed to 100, which is incompatible with a GigabitEthernet interface.

Answer

Replace SFP with 1000BASE-SX, configure 'negotiation auto' on GigabitEthernet0/0, and keep 'speed 1000' and 'duplex full'.

Answer

Replace SFP with 1000BASE-LX, configure 'negotiation auto' on GigabitEthernet0/0, and keep 'speed 1000' and 'duplex full'.

Answer

Replace SFP with 1000BASE-LX, configure 'no negotiation auto' on GigabitEthernet0/0, and configure 'speed 100' and 'duplex full'.

Question 4

You are troubleshooting a link between R1 (G0/0) and R2 (G0/0). The link is up but experiencing packet loss. You suspect an interface speed/duplex mismatch or SFP issue. Configure R1's interface to match the correct speed and duplex, and replace the SFP module if necessary to support a required distance of 40 km over single-mode fiber.

Accepted Answer

Remove manual speed/duplex settings, enable auto-negotiation, and replace the SFP with a long-reach module (e.g., 1000BASE-ZX) that supports 40 km over single-mode fiber.. The link is experiencing packet loss, likely due to a speed/duplex mismatch between the manually configured interface and the peer (which may use auto-negotiation) and/or an SFP module that cannot support the required 40 km distance over single-mode fiber. To resolve both potential issues, remove any manual speed and duplex settings to restore default auto-negotiation (using 'no speed' and 'no duplex'), and replace the SFP with a module rated for 40 km or more on SMF, such as a 1000BASE-ZX (or 1000BASE-EX) transceiver. Standard 1000BASE-LX/LH only reaches up to 10 km on SMF, so it is insufficient for this scenario.

Answer

Change the duplex to full and speed to 1000 Mbps manually, and keep the existing SFP.

Answer

Keep the manual speed/duplex settings but replace the SFP with a 1000BASE-SX module.

Answer

Enable auto-negotiation on both ends but keep the existing SFP.

Question 5

You are connected to R1 via console. R1 is directly connected to R2 over a 1000BASE-T link that is failing to come up. Configure interface GigabitEthernet0/0 on R1 with the correct speed and duplex settings to match R2's configuration, and then verify the link is operational. Additionally, determine the appropriate SFP type for a new 40 km fiber link between R1 and R2.

Accepted Answer

Configure interface GigabitEthernet0/0 with 'speed 1000' and 'duplex full'. For the new fiber link, use a 1000BASE-ZX SFP.. The link is down because R1 is set to auto-negotiate speed and duplex while R2 is hardcoded to 1000 Mbps full duplex. This mismatch causes the link to fail. To fix, configure R1's GigabitEthernet0/0 with 'speed 1000' and 'duplex full'. For the new 40 km fiber link, a 1000BASE-ZX SFP is required as it supports distances up to 70 km. (1000BASE-LX supports only up to 10 km and is insufficient for 40 km.) Verify with 'show interfaces GigabitEthernet0/0' to see the link state change to up/up.

Answer

Configure interface GigabitEthernet0/0 with 'speed auto' and 'duplex auto'. For the new fiber link, use a 1000BASE-SX SFP.

Answer

Configure interface GigabitEthernet0/0 with 'speed 1000' and 'duplex half'. For the new fiber link, use a 1000BASE-LX SFP.

Answer

Configure interface GigabitEthernet0/0 with 'speed 100' and 'duplex full'. For the new fiber link, use a 1000BASE-EX SFP.

Question 6

You are connected to R1. The link between R1's GigabitEthernet0/0 and R2's GigabitEthernet0/0 should operate at 1 Gbps full duplex, but the interface is showing errors and only negotiating at 100 Mbps half duplex. Diagnose and fix the fault, then verify the link is stable at the correct speed and duplex.

Accepted Answer

Remove the manual speed and duplex settings on R1's GigabitEthernet0/0 with 'no speed' and 'no duplex' to allow auto-negotiation.. The interface was manually configured with 'duplex half' and 'speed 100', which forced the link to 100 Mbps half duplex, causing CRC errors due to duplex mismatch. The correct fix is to remove these manual settings and allow auto-negotiation, or explicitly set both sides to 'speed 1000' and 'duplex full'. Since the remote side (R2) is set to auto (default), the simplest correction is to use 'no duplex' and 'no speed' on R1 to re-enable auto-negotiation. After the commands are applied, the interface should show 'Full-duplex, 1000Mb/s' and CRC errors should stop incrementing.

Answer

Change the duplex setting to 'full' and speed to '1000' on R1's GigabitEthernet0/0.

Answer

Replace the cable between R1 and R2 with a crossover cable.

Answer

Configure R2's GigabitEthernet0/0 with 'speed 100' and 'duplex half' to match R1's settings.

Question 7

You are connected to R1 via console. The link between R1 and R2 is experiencing packet loss and CRC errors. Configure interface speed and duplex on R1's GigabitEthernet0/0 to match R2's settings, then replace the SFP module with one that supports the required 2 km distance. Finally, verify the interface is operational without errors.

Accepted Answer

Configure speed 1000, duplex full, and no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.. The CRC errors indicate a duplex mismatch or faulty medium. R1 is set to auto-negotiation while R2 is hardcoded to 1000/full, causing mismatch. First, set speed and duplex on R1 to match R2: 'speed 1000' and 'duplex full'. Also disable auto-negotiation with 'no negotiation auto'. The existing SFP-GE-SX only supports 550m, but the link requires 2 km; replace it with a 1000BASE-LX/LH SFP (SFP-GE-L) which supports up to 10 km. After changes, verify with 'show interfaces Gi0/0' to confirm no CRC errors and correct speed/duplex.

Answer

Configure speed 1000 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-SX-MM.

Answer

Configure speed 100 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

Answer

Configure no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

Question 8

You are connected to SW1 via the console. The network uses VLANs 10 (Sales) and 20 (Engineering). A new switch SW2 is connected to SW1 via G0/1. You need to enable CDP to discover neighbor devices and verify that SW1 sees SW2. Currently, CDP is disabled globally.

Accepted Answer

Enable CDP globally with 'cdp run' and verify with 'show cdp neighbors'.. CDP is disabled globally with 'no cdp run'. Re-enabling with 'cdp run' allows SW1 to discover directly connected Cisco devices, including SW2. Option B is incorrect because interface-level 'cdp enable' requires CDP to already be enabled globally; since CDP is globally disabled, this command has no effect. Option C is incorrect because 'show cdp interface' displays CDP parameters per interface, not the neighbor table; you need 'show cdp neighbors' to see discovered devices. Option D is incorrect because 'cdp enable' is not a valid global command; the correct global command is 'cdp run'.

Answer

Enable CDP on interface G0/1 with 'cdp enable' and verify with 'show cdp neighbors'.

Answer

Enable CDP globally with 'cdp run' and verify with 'show cdp interface'.

Answer

Enable CDP globally with 'cdp enable' and verify with 'show cdp neighbors'.

Question 9

You are connected to R1 via the console. R1 is a new router that needs to be configured with a hostname, an encrypted privileged password 'cisco123', and a banner message 'Unauthorized access prohibited'. Additionally, SSH must be enabled for remote management using a domain name 'example.com' and a key size of 1024. The management interface is G0/0 with IP 192.168.1.1/24.

Accepted Answer

hostname R1
enable secret cisco123
banner motd #Unauthorized access prohibited#
ip domain-name example.com
crypto key generate rsa modulus 1024
line vty 0 4
transport input ssh
login local
username admin secret cisco123
interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown. It includes all required commands: hostname, enable secret (encrypted), banner motd, ip domain-name, crypto key, line vty with transport input ssh and login local, and a local user 'admin' with secret. The stem requires an encrypted privileged password (enable secret) and SSH, but SSH login local needs a local user. Option A lacks the username command, so SSH login would fail. Option B uses unencrypted enable password and incorrect VTY authentication. Option C has both password and login local, which is contradictory. Option D is the only complete configuration.

Answer

hostname R1
enable secret cisco123
banner motd #Unauthorized access prohibited#
ip domain-name example.com
crypto key generate rsa modulus 1024
line vty 0 4
transport input ssh
login local
interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

Answer

hostname R1
enable password cisco123
banner motd #Unauthorized access prohibited#
ip domain-name example.com
crypto key generate rsa modulus 1024
line vty 0 4
transport input ssh
password cisco123
login
interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

Answer

hostname R1
enable secret cisco123
banner motd #Unauthorized access prohibited#
ip domain-name example.com
crypto key generate rsa modulus 1024
line vty 0 4
transport input ssh
password cisco123
login local
interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

Question 10

You are connected to the console of R1. The network has a point-to-point serial link between R1 and R2. The link is down and the line protocol is down. The cable is a DCE/DTE crossover, and R1 is the DCE. The initial configuration shows the interface with an IP address but no clock rate set.

Accepted Answer

Configure the clock rate on R1's serial interface.. On a serial DCE cable, the DCE end must configure a clock rate to provide timing. Without it, the line protocol stays down. Setting 'clock rate 128000' on R1 resolved the issue.

Answer

Configure the clock rate on R2's serial interface.

Answer

Replace the serial cable with a straight-through cable.

Answer

Set the encapsulation on both ends to PPP.

Question 11

You are connected to the console of R1. The network team wants to secure remote access. R1 currently has no SSH configuration. The domain name is 'example.com' and you need to generate an RSA key pair of 2048 bits and enable SSH version 2 on vty lines.

Accepted Answer

Configure IP domain name, generate RSA key pair with 2048 bits, set SSH version 2, and configure vty lines to use SSH.. Enabling SSH on a Cisco router requires four steps: set a hostname and IP domain name (needed to generate the RSA key pair), generate the RSA crypto key with the specified modulus (2048 bits), set the SSH version to 2, and configure the vty lines with 'transport input ssh' and a local username. All four are mandatory; omitting any one leaves SSH non-functional.

Answer

Generate RSA key pair with 2048 bits, set SSH version 2, and configure vty lines to use SSH. Domain name is optional.

Answer

Configure IP domain name, generate RSA key pair with 2048 bits, and set SSH version 2. No need to configure vty lines.

Answer

Configure IP domain name, generate RSA key pair with 1024 bits, set SSH version 2, and configure vty lines to use SSH.

Question 12

You are connected to the console of R1. The network uses IPv6 with EUI-64. R1's GigabitEthernet0/0 interface has MAC address 0011.2233.4455. You must configure the interface to generate an IPv6 link-local address using the 'ipv6 enable' command, and also assign a global unicast address 2001:db8:1::/64 using EUI-64. The interface is currently administratively down.

Accepted Answer

R1(config-if)# ipv6 enable
R1(config-if)# ipv6 address 2001:db8:1::/64 eui-64
R1(config-if)# no shutdown. The ipv6 enable command explicitly creates a link-local address as required by the scenario. The global unicast address with the eui-64 keyword automatically derives the interface ID from the MAC address. Option B is incorrect because it tries to manually configure a link-local address with eui-64, which is unnecessary and invalid. Option C omits the ipv6 enable command, failing the explicit requirement. Option D assigns a static host portion instead of using eui-64.

Answer

R1(config-if)# ipv6 address fe80::/10 eui-64
R1(config-if)# ipv6 address 2001:db8:1::/64 eui-64
R1(config-if)# no shutdown

Answer

R1(config-if)# ipv6 address 2001:db8:1::/64 eui-64
R1(config-if)# no shutdown

Answer

R1(config-if)# ipv6 enable
R1(config-if)# ipv6 address 2001:db8:1::1/64
R1(config-if)# no shutdown

Question 13

You are connected to the console of R1. The network administrator reports that R1 cannot discover neighboring devices via CDP. R1 is connected to SW1 via GigabitEthernet0/0. You suspect CDP is disabled globally or on the interface. Your task is to enable CDP and verify neighbor discovery.

Accepted Answer

Enter global configuration mode, issue 'cdp run', then enter interface configuration mode for GigabitEthernet0/0 and issue 'cdp enable'.. CDP was disabled globally and on the interface. Enabling CDP globally and then on the interface allows R1 to discover directly connected Cisco devices.

Answer

Enter global configuration mode, issue 'cdp enable', then enter interface configuration mode for GigabitEthernet0/0 and issue 'cdp run'.

Answer

Enter global configuration mode, issue 'cdp run', then enter interface configuration mode for GigabitEthernet0/0 and issue 'no cdp disable'.

Answer

Enter global configuration mode, issue 'cdp enable', then enter interface configuration mode for GigabitEthernet0/0 and issue 'no cdp disable'.

Question 14

You are connected to the console of R1. The output of 'show interfaces serial0/0/0' displays that the interface is administratively down (status: administratively down, line protocol is down). The network administrator reports that the serial link between R1 and R2 was recently configured but is not working. You need to troubleshoot and restore connectivity. The serial interface on R1 is Serial0/0/0, and the link is a point-to-point HDLC connection.

Accepted Answer

Enter interface configuration mode for Serial0/0/0 and issue the 'no shutdown' command.. The status 'administratively down' on a Cisco interface means the interface has been manually disabled with the shutdown command. The fix is to enter interface configuration mode for Serial0/0/0 and issue no shutdown, which brings the interface up and allows the line protocol to initialize. This is the direct cause of the reported link failure.

Answer

Enter global configuration mode and issue the 'clock rate 64000' command.

Answer

Enter interface configuration mode for Serial0/0/0 and issue the 'encapsulation ppp' command.

Answer

Enter privileged EXEC mode and issue the 'clear interface serial0/0/0' command.

Question 15

You are connected to the console of SW1. The network administrator reports that a workstation connected to interface FastEthernet0/1 cannot communicate with the rest of the network. The workstation is configured for VLAN 10, but the interface is in VLAN 1.

Accepted Answer

Configure the interface as an access port and assign it to VLAN 10.. The workstation is configured for VLAN 10, but the switch interface is in VLAN 1. To restore connectivity, the interface must be configured as an access port and assigned to VLAN 10, matching the workstation's VLAN. This places the port in the correct broadcast domain so the workstation can communicate with other VLAN 10 devices and its gateway.

Answer

Configure the interface as a trunk port.

Answer

Configure the interface as a trunk port and allow VLAN 10.

Answer

Configure the interface as a dynamic desirable port.

CCNA Network Infrastructure and Connectivity Practice Test 24 — 15 Questions

Exhibit

CCNA Network Infrastructure and Connectivity Practice Test 24 — 15 Questions

Exhibit