Question 1

Finding the IOS software release On a Cisco router, which EXEC command shows the running IOS version along with platform details and uptime?

Accepted Answer

Introduction / Context: Knowing the exact Cisco IOS version helps with feature verification, bug checks, and compatibility planning. The router provides several show commands, but only one displays the software image version string, build information, uptime, and often the system bootstrap and configuration register in one place. Given Data / Assumptions: You have user or privileged EXEC access to the router. You need to view the current IOS version running in RAM. Flash contents and running configuration are separate concerns. Concept / Approach: The command show version reports the IOS image name and version, device uptime, processor type, memory, and configuration register. While show flash can list stored images, and show running-config shows configuration, neither displays the active software release as clearly as show version. Step-by-Step Solution: Enter privileged EXEC mode if necessary.Issue: show version.Note the version string (for example, 15.2(4)M8) and image filename.Record additional details such as uptime and configuration register. Verification / Alternative check: Cross-check image filename reported by show version with files listed by show flash to confirm where the image was booted from. If ROMMON boot is suspected, the output also indicates the ROM monitor version. Why Other Options Are Wrong: sh IOS and sh software are not standard IOS commands. sh flash lists images in storage but not necessarily the active version. sh running-config displays configuration, not the software release. Common Pitfalls: Confusing stored images with the running image; a router can have multiple images in flash. Overlooking configuration register settings that might affect next boot behavior. Final Answer: sh version

Question 2

Understanding the o/r 0x2142 command In ROM Monitor or during password recovery, what does setting the configuration register to 0x2142 (for example via 'o/r 0x2142') accomplish on a Cisco router?

Accepted Answer

Introduction / Context: Password recovery and emergency maintenance sometimes require booting a router without loading the startup-config from NVRAM. Cisco devices use a configuration register that influences boot behavior. Setting it to a special value, commonly 0x2142, instructs the router to ignore NVRAM at next boot, allowing administrators to safely enter and change passwords and other settings. Given Data / Assumptions: You can access ROMMON (ROM Monitor) or otherwise set the configuration register. You intend to preserve but temporarily bypass the startup-config. The device will be reloaded after the change. Concept / Approach: The configuration register's low-order bits control boot behavior. Value 0x2142 tells IOS to ignore the NVRAM startup-config upon boot. After the router boots to default settings, you can copy the saved configuration into running-config, reset passwords, and then restore the register to the normal 0x2102 before saving and reloading. Step-by-Step Solution: In ROMMON, set: confreg 0x2142 (or o/r 0x2142 depending on platform).Reload the router; it will boot without applying startup-config.Enter privileged mode and copy saved config if needed: copy startup-config running-config.Change passwords, then set confreg back to 0x2102 and write memory. Verification / Alternative check: show version displays the current configuration register. After fixes, confirming 0x2102 ensures normal boots will use the startup-config again. Why Other Options Are Wrong: Restarting, entering ROMMON, or viewing a lost password are not the direct effects of 0x2142. Forcing ROM image boot is controlled by other config-register bits and boot statements, not strictly 0x2142. Common Pitfalls: Forgetting to revert to 0x2102, causing future boots to ignore configuration. Accidentally overwriting the original configuration by saving before copying it into running-config. Final Answer: It is used to bypass the configuration in NVRAM.

Question 3

Loading a new IOS image Which command copies a Cisco IOS software image from a TFTP server into flash memory on the router?

Accepted Answer

Introduction / Context: Upgrading a Cisco router's operating system typically involves transferring an image file into flash storage. The router supports multiple file transfer protocols; TFTP is common in lab and controlled environments. Knowing the correct source and destination order in the copy command prevents accidental overwrites and failed upgrades. Given Data / Assumptions: A TFTP server is reachable over IP and hosts the new IOS image. The router has sufficient flash capacity or old images are managed appropriately. You are in EXEC or privileged EXEC mode. Concept / Approach: The IOS copy command syntax is copy . To bring an image from a TFTP server into flash, the correct order is copy tftp flash. You will be prompted for the server IP and filename. After validation and checksum, the image is written into flash and can be made the boot image via the boot system command or default selection rules. Step-by-Step Solution: Verify connectivity to the TFTP server (for example, ping).Issue: copy tftp flash.Provide server address and image filename when prompted.Wait for the transfer to complete and verify file size and integrity. Verification / Alternative check: Use show flash to confirm the new image file and available space. Use show version to check the next boot image after setting boot system statements if necessary. Why Other Options Are Wrong: copy flash tftp exports from flash to a TFTP server (reverse direction). copy ftp flash is valid for FTP, not TFTP; however, it does not match the TFTP scenario assumed by the question. copy flash ftp is reverse direction for FTP. copy usbflash0: flash: may be valid on platforms with USB, but the question specifies TFTP. Common Pitfalls: Mistyping the filename or insufficient flash space causes failures. Forgetting to update the boot variable, resulting in booting the old image after reload. Final Answer: copy tftp flash

Question 4

Checking flash usage before an IOS upgrade Which command shows the files stored in flash, their sizes, and remaining free space so you can verify whether the current IOS image and a new image can coexist in flash memory?

Accepted Answer

Introduction / Context: Before upgrading IOS, you need to ensure enough flash storage is available to hold both the existing and new images (or at least the new one). Cisco IOS provides commands to list files, sizes, and free space in flash so you can plan the upgrade path accordingly without risking an interruption or incomplete transfer. Given Data / Assumptions: You want to retain the current working image during the upgrade. Flash is the storage medium for IOS images on the device. You need to confirm total and free flash capacity and file sizes. Concept / Approach: show flash displays flash directories, file names, sizes, and the amount of free space. This output lets you decide whether to delete old images, expand storage, or proceed with a parallel image. Although dir flash: is also commonly available, exam objectives and many platforms emphasize show flash as the canonical command. Step-by-Step Solution: Issue: show flash.Note the size of the current IOS image file (for example, .bin file) and total available bytes free.Compare the new image size to free space to determine if both images can coexist.If insufficient space, plan to delete old files or use an alternate method (external storage or direct replacement). Verification / Alternative check: After copying the new image, run show flash again to confirm its presence and remaining free bytes. Use show version to verify the boot variable and configuration register for next reload behavior. Why Other Options Are Wrong: show version reports the running image but not detailed flash utilization. show memory concerns RAM/processor memory, not flash storage. show buffers shows I/O buffer stats, unrelated to flash. dir flash: can work on many platforms, but the question seeks the canonical command specifically called out in many study guides: show flash. Common Pitfalls: Confusing RAM (where IOS runs) with flash (where IOS is stored). Not verifying free space before the copy, leading to partial transfers. Final Answer: show flash

Question 5

Isolating a routing-path failure You suspect an intermediate router is dropping traffic to a remote network. Which user EXEC command helps you identify the hop at which packets stop being forwarded?

Accepted Answer

Introduction / Context: When a destination is unreachable, you must determine where along the path packets are being dropped. Tools that probe each hop and report incremental results are essential to isolate the failing segment. On Cisco devices, traceroute (often abbreviated as trace in user EXEC) performs this function by using increasing TTL values and listening for time-exceeded messages from intermediate routers. Given Data / Assumptions: You have user EXEC access (prompt shows Router>). You want to identify the hop count and the node at which forwarding fails. ICMP is not being filtered along the path (or UDP probe responses are permitted). Concept / Approach: traceroute sends probe packets with incrementing TTL starting at 1. Each router that decrements the TTL to zero returns an ICMP time-exceeded message, revealing its identity. When a hop fails to respond or a later hop is reachable, you can infer where the issue lies. While ping only tells you if an endpoint responds, traceroute shows the entire path, which is far more diagnostic when dealing with multi-hop networks. Step-by-Step Solution: From user EXEC, enter: trace (or traceroute ).Observe responding hops and note where responses cease.Correlate the failing hop with routing tables and interface status on that device.Remediate (fix routes, ACLs, or interface issues) at or before the failing hop. Verification / Alternative check: Use show ip route on the suspect router to verify that a route exists. Confirm with ping sourced from intermediate routers to isolate asymmetric issues. Why Other Options Are Wrong: ping tests reachability but not path details. show ip route and show interface provide static information and do not reveal the failing hop across the path. pathcheck is not a standard IOS command. Common Pitfalls: Interpreting asterisks as absolute failure; some networks rate-limit or block TTL-exceeded responses. Forgetting that traceroute behavior can vary by platform (UDP vs ICMP probes). Final Answer: Router> trace

Question 6

Why a copied running configuration might not work You copied a configuration from a network host into the router's RAM (running-config). The configuration looks correct, but nothing works. What is the most likely cause in this scenario?

Accepted Answer

Introduction / Context: On Cisco devices, interface state is an explicit configuration element. If an interface is administratively shut down, it will remain down until a no shutdown command is applied, even if you paste or merge a configuration that contains IP addressing and other settings. Understanding merge semantics explains why a seemingly correct running-config may not pass traffic after being copied in. Given Data / Assumptions: You copied a valid-looking configuration into running-config (RAM). Interfaces still show administratively down (or line protocol down). No device reload occurred; the configuration was merged, not replaced. Concept / Approach: Copying or pasting configuration lines merges with the existing running-config; it does not automatically negate pre-existing commands. If an interface previously had the shutdown directive, and your pasted configuration did not include no shutdown, the interface will remain disabled. This is a common oversight when restoring configurations on lab or field devices. Step-by-Step Solution: Check interface status with: show interfaces status or show ip interface brief.If interfaces are administratively down, enter interface configuration mode.Apply: no shutdown on each required interface.Verify link and protocol come up; confirm routing neighbors form as expected. Verification / Alternative check: Use show running-config to ensure no shutdown is present. Confirm L1/L2 status with show interfaces and end-to-end pings or routing adjacencies forming (for example, show ip ospf neighbor). Why Other Options Are Wrong: Wrong config (A) is possible but not the most likely reason when the pasted lines look correct. Copying into flash (B) would not alter running-config at all; the prompt states you copied into RAM. IOS corruption (D) or ROMMON fallback (E) would present different symptoms (reboots, missing commands, or ROMMON prompt). Common Pitfalls: Assuming copy replaces instead of merges; always include necessary no statements (like no shutdown). Forgetting to save changes to startup-config using write memory or copy run start. Final Answer: The copy did not override the shutdown command in running-config.

Question 7

Cisco IOS Telnet multitasking: If you want to keep an existing Telnet session connected and start another one from the same router, which key combination suspends the current Telnet and returns you to the router prompt so you can open a second sessi…

Accepted Answer

Introduction / Context: In Cisco IOS, administrators often need to manage more than one Telnet session at the same time. Knowing the correct escape sequence lets you suspend a current Telnet connection without disconnecting it, return to the router prompt, and initiate an additional Telnet session. Given Data / Assumptions: You are connected to a remote device via Telnet from a Cisco router or switch. You want to keep the first session active while starting a second one. IOS default key bindings are in use (no custom terminal mappings). Concept / Approach: IOS provides a Telnet escape sequence. The default is pressing Ctrl+Shift+6 followed by X. This suspends the active Telnet session, returning you to the local IOS prompt. You can then open new sessions, resume existing ones with the 'resume' command, or close them with 'disconnect'. Step-by-Step Solution: From within an active Telnet session, press and hold Ctrl+Shift and tap 6.Release the keys and press X.You are returned to the IOS prompt without dropping the Telnet session.Start a second Telnet using 'telnet ' or 'ssh ' as needed.Use 'show sessions' to list suspended sessions, 'resume ' to switch back, or 'disconnect ' to close one. Verification / Alternative check: Run 'show sessions' to confirm the first Telnet session remains open. You should see one or more connections listed with line numbers and hosts. Why Other Options Are Wrong: Tab+Spacebar: Not an IOS escape sequence. Common Pitfalls: Mixing up the order (pressing X before Ctrl+Shift+6) or forgetting to release keys before pressing X will not trigger the escape. Also, some terminal emulators may remap Ctrl+6; verify key mappings if it fails. Final Answer: Ctrl+Shift+6, then X

Question 8

Before applying a fresh startup configuration: You connect to a newly delivered router and discover an existing configuration in place. What should you do prior to entering a new configuration?

Accepted Answer

Introduction / Context: Decommissioned or lab-used routers often ship with old startup-config files in NVRAM. Loading a fresh configuration requires clearing these remnants to avoid inherited passwords, access lists, or routing processes that could conflict with your design. Given Data / Assumptions: An unexpected configuration is present on a Cisco router. You intend to deploy a clean, known-good configuration. Standard IOS behavior and storage locations apply (startup-config in NVRAM, IOS in flash). Concept / Approach: The startup-config is stored in Non-Volatile RAM (NVRAM). To ensure a clean slate, erase the startup-config and then reload the router so it boots without a saved configuration (setup mode). After the reload, you can paste or load the new configuration and save it back to NVRAM. Step-by-Step Solution: From privileged EXEC: 'write erase' or 'erase startup-config'.Confirm the erase when prompted.Reload the router with 'reload' and do not save the running-config when asked.After reboot, enter global configuration mode and apply your new configuration.Save the configuration with 'copy running-config startup-config'. Verification / Alternative check: Use 'show startup-config' (should be empty before reload) and 'show version' to confirm normal boot. After loading your config, 'show running-config' and 'show startup-config' should match. Why Other Options Are Wrong: Erase RAM/Flash: RAM is volatile and does not store configs; Flash holds the IOS image, which you typically keep. Enter new config and save: Risk of merging with legacy settings, causing outages. Common Pitfalls: Accidentally erasing flash or saving over an undesired running-config before the erase/reload step. Final Answer: NVRAM should be erased and the router restarted.

Question 9

Finding a remote Cisco device's management IP: You need the IP address of a remote switch (reachable over a connected router). Which IOS command on the adjacent router reveals the neighbor's IP address directly via Cisco Discovery Protocol (CDP)?

Accepted Answer

Introduction / Context: When managing distributed networks, quickly discovering a connected Cisco device's IP address is invaluable. Cisco Discovery Protocol (CDP) lets directly connected Cisco devices advertise identity, platform, port, and management IP information. Given Data / Assumptions: The router is directly connected to the target switch. CDP is enabled on both interfaces and devices. You need the switch's IP for remote management (Telnet/SSH/SNMP). Concept / Approach: 'show cdp neighbors' summarizes neighbors but typically does not list their IP address. The detailed form, 'show cdp neighbors detail', includes the Device-ID, platform, local/remote ports, and the Management address (IP), which is exactly what you need. Step-by-Step Solution: On the adjacent router, enter privileged EXEC mode.Run 'show cdp neighbors detail'.Locate the 'Management address(es):' or 'IP address:' field in the output for the target neighbor.Use that IP to Telnet/SSH or to update documentation. Verification / Alternative check: Ping the retrieved IP. If needed, run 'show lldp neighbors detail' in mixed-vendor environments using LLDP. Why Other Options Are Wrong: show ip arp: Shows IP-to-MAC mappings learned on L3 interfaces; may not include the switch SVI if not recently communicated. show ip route: Displays routes, not neighbor IPs. show cdp neighbor: Summary view; usually lacks the IP field. Common Pitfalls: CDP disabled globally or on the interface, or management VLAN SVI shut down on the switch will prevent seeing a useful IP. Final Answer: Issue the show cdp neighbors detail command on the router connected to the switch.

Question 10

Troubleshooting failed Telnet access to a remote device: Which of the following could be the cause? Consider addressing, filtering, cabling, and VTY configuration.

Accepted Answer

Introduction / Context: Telnet connection failures can originate from multiple layers of the OSI model and from device configuration. Effective troubleshooting requires checking logical addressing, control-plane filters, physical connectivity, and line (VTY) configuration. Given Data / Assumptions: Potential issues listed: (1) IP addresses are incorrect, (2) an ACL is filtering Telnet, (3) a defective serial cable, (4) the VTY password is missing. Remote access is attempted via Telnet. Standard Cisco IOS behavior for VTY lines and ACLs. Concept / Approach: Telnet requires IP connectivity end to end and an allowed control-plane path to VTY lines with correct authorization. Any single failure among addressing, reachability, filtering, or line authentication can prevent a session from establishing. Step-by-Step Solution: Check L3 reachability: verify correct IP addresses and masks (Issue 1).Confirm physical path: layer-1/2 health (defective serial or media) can break IP reachability (Issue 3).Inspect control-plane filters: inbound ACLs on interfaces or 'access-class' on VTY lines can block TCP port 23 (Issue 2).Validate VTY configuration: missing password or AAA settings can deny login (Issue 4). Verification / Alternative check: Use 'ping' and 'traceroute' for reachability, 'show interfaces' for physical health, 'show access-lists' and interface configs for filters, and 'show run | section line vty' to review VTY settings. Why Other Options Are Wrong: 1 only / 3 only / 2 and 4 only: Each subset ignores other equally plausible causes. Telnet failures are multi-factor; all listed can cause failure. Common Pitfalls: Forgetting that line-level restrictions ('transport input') or AAA misconfigurations also block Telnet; assuming L3 pings imply Telnet must work (port 23 may still be filtered). Final Answer: All of the above

Question 11

Checking LAN connectivity from a router: Which three IOS commands are most useful for diagnosing local network issues among the following list? (1) show interfaces  (2) show ip route  (3) tracert  (4) ping  (5) dns lookups

Accepted Answer

Introduction / Context: When LAN connectivity problems arise, Cisco IOS offers show and exec tools that validate interface status, routing, and active reachability. Selecting the right set accelerates troubleshooting and reduces downtime. Given Data / Assumptions: Candidate commands: show interfaces, show ip route, tracert, ping, dns lookups. You are working from a Cisco router CLI. Objective: diagnose LAN link health and IP reachability. Concept / Approach: 'show interfaces' verifies Layer 1/2 state, errors, and duplex/speed. 'show ip route' confirms Layer 3 networks known to the router. 'ping' tests end-to-end IP connectivity and can use extended options (source interface, repeat count). 'tracert' is a Windows command; IOS uses 'traceroute'. 'dns lookups' is not a standard troubleshooting command name (IOS uses 'ip domain-lookup' to enable/disable DNS resolution). Step-by-Step Solution: Run 'show interfaces' to inspect up/down, CRC errors, late collisions, and queue drops.Run 'show ip route' to verify local VLANs/subnets are present and have correct next hops.Use 'ping' to test host or gateway reachability; if it fails, use extended ping with a specific source. Verification / Alternative check: Optionally run 'traceroute' (IOS spelling) to isolate the failing hop; use 'show arp' for L2/L3 bindings if ARP resolution is suspect. Why Other Options Are Wrong: 2 and 5 / 3 and 5: 'dns lookups' is not a diagnostic command; 'tracert' is not the IOS keyword. None of the above: Incorrect because 1, 2, and 4 are highly effective on IOS. Common Pitfalls: Leaving DNS lookup enabled can cause typos to hang CLI while IOS attempts name resolution; disable with 'no ip domain-lookup' during troubleshooting. Final Answer: 1 ,2 and 4

Question 12

Ending a Telnet session from a router: After making changes during a Telnet session, which command properly closes the session and returns you to the local IOS prompt?

Accepted Answer

Introduction / Context: Once remote administration is complete, the Telnet session should be ended cleanly. IOS provides several commands for line management, but only one is correct for gracefully terminating an active Telnet. Given Data / Assumptions: You are in user/privileged EXEC mode on a remote device accessed via Telnet. You want to terminate the session and return to the original local router's prompt. Concept / Approach: The 'exit' command is used within the Telnet session to close the connection. This differs from 'disconnect' (used from the local router's session management prompt) and from 'close'/'disable' which are not valid IOS commands in this context. Step-by-Step Solution: While connected to the remote device, type 'exit' and press Enter.This closes the Telnet session and returns you to the previous router's EXEC prompt.If multiple sessions are active, you may instead use 'Ctrl+Shift+6, then X' to suspend and 'disconnect <line#>' at the local prompt. Verification / Alternative check: Prompt should change back to the local device's hostname. 'show sessions' should confirm the closed session is gone. Why Other Options Are Wrong: disconnect: Used at local IOS prompt after suspending sessions. close/disable: Not valid Telnet termination commands in IOS. Common Pitfalls: Typing 'quit' (works in some contexts) or forgetting to save changes before exiting, causing config loss. Final Answer: exit

Question 13

Debugging Telnet sessions: You Telnet into a remote Cisco device and run the command debug ip rip, but no debug output appears. What is the likely reason?

Accepted Answer

Introduction / Context: In Cisco IOS, debug output by default goes to the console port. When connected through Telnet or SSH, you will not see debug messages unless you explicitly enable logging to the vty session. Given Data / Assumptions: You Telnet into a remote router. You issue a debug command (e.g., debug ip rip). No debug output is displayed in your Telnet session. Concept / Approach: To view debug output remotely, you must run 'terminal monitor'. This command enables the display of log/debug messages on your VTY session. Without it, all debug output is still sent to the console only. Step-by-Step Solution: Telnet into the router and enter privileged EXEC mode.Run 'terminal monitor' to enable logging to the VTY line.Re-run the debug command (e.g., debug ip rip).Now, you will see the expected debug output in your Telnet session. Verification / Alternative check: Test by sending RIP updates (e.g., clear ip route *) and observe debug lines appear. Run 'terminal no monitor' to turn it off afterward. Why Other Options Are Wrong: show ip rip: A display command; not related. IP addressing incorrect: Would not suppress all debug output. Debug only console: True by default, but terminal monitor overrides this behavior. Common Pitfalls: Forgetting to disable debugs after use can overwhelm CPU and crash the router. Always use 'undebug all' or 'u all' when finished. Final Answer: You must use the terminal monitor command.

Question 14

Backing up IOS software: Which IOS command copies the router's current IOS image from flash memory to a backup TFTP server on the network?

Accepted Answer

Introduction / Context: Backing up the IOS image is part of disaster recovery. The IOS is stored in flash memory and can be transferred to a TFTP server for safekeeping before upgrades or hardware changes. Given Data / Assumptions: You want to save the IOS image from flash. A TFTP server is reachable on the network. Router has IP connectivity to the TFTP server. Concept / Approach: The command 'copy flash tftp' prompts for the source filename (IOS image) and destination IP address, then transfers the file via TFTP. 'copy run start' saves the configuration only, not IOS. 'copy start tftp' saves startup-config to TFTP, not IOS. Step-by-Step Solution: Enter privileged EXEC mode.Type 'copy flash tftp'.Enter the source filename (e.g., c1900-universalk9-mz.SPA.152-4.M3.bin).Enter the TFTP server IP (e.g., 172.16.10.1).Wait for the copy confirmation message. Verification / Alternative check: On the TFTP server, verify the IOS binary appears and file size matches the flash image. Why Other Options Are Wrong: transfer IOS to ...: Not a valid IOS command. copy run start / copy start tftp: Deal with configs, not IOS. copy flash tftp: Correct. Common Pitfalls: Ensure TFTP server is reachable and allows write permissions. Also verify sufficient storage space on the server. Final Answer: copy flash tftp

Question 15

Viewing the configuration register: Which IOS command displays the current configuration register value that controls how the router boots?

Accepted Answer

Introduction / Context: The configuration register controls how the router boots: from flash, from ROMMON, or from a TFTP server. It also influences console baud rate and password recovery. Knowing how to view it helps troubleshoot boot issues. Given Data / Assumptions: You are diagnosing boot sequence or password recovery on a Cisco router. You need to verify the config-register value (commonly 0x2102). Concept / Approach: The 'show version' command displays IOS version, uptime, image file, and the configuration register setting. This is the authoritative way to check the register value from within IOS. Step-by-Step Solution: Enter privileged EXEC mode.Run 'show version'.Scroll to the bottom of the output.Locate the line 'Configuration register is 0x2102'. Verification / Alternative check: From ROMMON mode, 'confreg' can show/change the value, but within IOS it is only visible in 'show version'. Why Other Options Are Wrong: show ip route: Displays routing table. show boot version / show flash: Not valid commands for this purpose. 'show flash' lists IOS images in flash, not config-register. Common Pitfalls: Confusing 'show running-config' with boot behavior; the config-register is not stored in running-config. Final Answer: show version

Question 16

Configuration register 0x2102: On a Cisco router, what does a configuration register value of 0x2102 instruct the device to do during boot?

Accepted Answer

Introduction / Context: The configuration register is a 16-bit value that directs how a Cisco router boots. The most common setting, 0x2102, tells the device to load the IOS from flash and the startup-config from NVRAM. Given Data / Assumptions: Configuration register = 0x2102. Standard Cisco IOS boot process. Concept / Approach: 0x2102 is the factory default. It specifies: use the console speed 9600, load IOS image from flash, and load the startup-config from NVRAM. Alternative values (0x2142) ignore NVRAM (for password recovery); 0x2100 boots ROMMON; 0x2101 boots RXBOOT. Step-by-Step Solution: Check register value with 'show version'.Interpret 0x2102: boot system commands are used (if present); otherwise default flash IOS is loaded.Startup-config in NVRAM is loaded after IOS boots. Verification / Alternative check: Change register with 'config-register' command in global config or 'confreg' in ROMMON if needed. Why Other Options Are Wrong: ROMMON: Value 0x2100. Password recovery: Value 0x2142 ignores NVRAM. TFTP boot: Requires boot system command + TFTP, not default 0x2102. Common Pitfalls: Misinterpreting 0x2142 vs 0x2102. 2142 is used for recovery, 2102 is default normal operation. Final Answer: Tells the router to look in NVRAM for the boot sequence

Question 17

Cisco IOS password recovery follow-up: After you successfully complete the password recovery procedure and want to return the router to normal boot behavior, what configuration register value should be set?

Accepted Answer

Introduction / Context: In Cisco routers, the configuration register controls key boot behaviors such as where to load the IOS and whether to ignore the startup configuration in NVRAM. During password recovery, the register is temporarily changed so the router ignores the saved configuration; after recovery, you must restore the normal value. Given Data / Assumptions: Password recovery has been completed. The goal is to restore normal operation (load startup-config on boot). Standard Cisco IOS behavior is assumed. Concept / Approach: The typical normal-operation value is 0x2102. The commonly used recovery value is 0x2142, which instructs the device to ignore NVRAM at the next boot so you can bypass passwords. Once finished, set the register back to 0x2102 so the router again loads the saved configuration on startup. Step-by-Step Solution: From privileged EXEC: enableEnter global config: configure terminalRestore register: config-register 0x2102Save and reload: copy running-config startup-config, then reload Verification / Alternative check: Use show version to verify the current configuration register value displayed near the end of the output. Confirm that on reboot the router reads the startup configuration as expected. Why Other Options Are Wrong: 0x2142 (D) is the temporary recovery setting that ignores NVRAM. 0x2100 and 0x2101 (A, B) alter boot behavior (e.g., ROMMON or image selection) and are not the default for normal operations. Common Pitfalls: Forgetting to change 0x2142 back to 0x2102, causing the router to keep ignoring the startup-config and booting blank. Final Answer: 0x2102

Question 18

Router boots with a blank configuration after saving: You executed 'copy running-config startup-config' and rebooted, but the router came up with an empty configuration. What is the most likely cause?

Accepted Answer

Introduction / Context: A Cisco router loading blank after you saved the configuration commonly indicates a configuration register problem. The register can instruct IOS to ignore startup-config, which is frequently used during password recovery and sometimes left unchanged by mistake. Given Data / Assumptions: 'copy running-config startup-config' completed successfully. After reboot, the router shows the initial configuration dialog or no saved settings. No intentional factory reset was performed. Concept / Approach: If the configuration register is 0x2142, the router ignores NVRAM on boot. This exactly produces a blank configuration despite valid contents in startup-config. Restoring the default 0x2102 re-enables reading startup-config at boot time. Step-by-Step Solution: Check register: show version (look for 'Configuration register')If 0x2142 (or another nonstandard value) is set, enter config mode.Set default: config-register 0x2102Write memory and reload: copy run start; reload Verification / Alternative check: After reload, the router should load the saved startup-config automatically. Confirm by checking interface IPs, routing processes, and banners. Why Other Options Are Wrong: NVRAM corruption (B) is possible but less common; most cases trace to the register. Incorrect boot command or IOS compatibility (A, D) typically affect image loading, not reading startup-config specifically. Common Pitfalls: Leaving 0x2142 set after password recovery; confusing boot variable (boot system) with the configuration register; not saving the corrected setting before reload. Final Answer: The configuration register setting is incorrect.

Question 19

Cisco IOS 'show hosts' output: Which items are reported by the 'show hosts' command on a router (choose the correct combination)?

Accepted Answer

Introduction / Context: The show hosts command displays the router’s hostname resolution information, including cached and statically defined mappings used when you ping or telnet by name instead of by IP address. Given Data / Assumptions: (1) Temporary DNS entries (2) Names of routers created using the hostname command (3) IP addresses of workstations allowed to access the router (4) Permanent name-to-address mappings created using the ip host command (5) Length of time a host has been connected via Telnet Concept / Approach: show hosts shows name resolution tables: cached DNS lookups and static mappings defined by ip host. It does not list access permissions, Telnet session durations, or the mere fact that you set the router’s own hostname. Step-by-Step Solution: Recognize valid outputs: temporary DNS cache (1); static mappings (4).Eliminate non-related items: (2) local hostname setting, (3) access lists or authorization, (5) session timers.Select the combination '1 and 4'. Verification / Alternative check: Run show hosts on a lab router with ip host entries defined and after a DNS lookup; observe both static and cached entries listed with their IPs and time-to-live values (for cached entries). Why Other Options Are Wrong: Combos including (2), (3), or (5) are incorrect because those items are not part of host name resolution tables. Common Pitfalls: Confusing show hosts with show users or show sessions; assuming router hostname settings appear in host tables; mixing up DNS features with access-control features. Final Answer: 1 and 4

Question 20

Copying IOS from flash to a laptop via TFTP (direct Ethernet connection): Your laptop is directly cabled to a router's Ethernet port to run 'copy flash tftp'. Which prerequisites must be met for the transfer to succeed?

Accepted Answer

Introduction / Context: To copy an image from router flash to a TFTP server on a laptop, basic IP connectivity and a running TFTP service on the laptop are required. The router acts as a TFTP client during this operation. Given Data / Assumptions: (1) TFTP server must run on the router – false. (2) TFTP server must run on the laptop – true. (3) The Ethernet cable must be straight-through – usually false for a direct old-style connection (crossover is traditional unless auto MDI-X is supported). (4) The laptop must be on the same IP subnet as the router’s Ethernet interface – true for a simple point-to-point link without routing. (5) The copy command must be supplied the laptop’s IP address – true; the router (client) needs the TFTP server address. Concept / Approach: Since the router is the TFTP client, the server process must exist on the laptop. With a direct cable and no routing, both interfaces should share a subnet. The command prompts for the remote host (TFTP server) IP, which is the laptop’s address. Step-by-Step Solution: Install/run TFTP server on the laptop (2).Assign IPs in the same subnet to laptop and router interface (4).From the router: copy flash tftp → enter the laptop’s IP when prompted (5). Verification / Alternative check: Ping the laptop from the router to verify connectivity. Ensure the TFTP server's working directory is writable. Observe file transfer progress and resulting file on the laptop. Why Other Options Are Wrong: (1) Router does not host the TFTP server for this operation. (3) Cable type depends on hardware; a straight-through is not a universal requirement for a direct PC-to-router link (traditionally crossover). Common Pitfalls: Blocked by host firewall on UDP 69; wrong TFTP root path; using the wrong cable on non-auto-MDI-X ports; forgetting to set matching subnets. Final Answer: 2, 4 and 5

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