Question 1

Cisco IOS default management lines: By default, how many simultaneous Telnet (VTY) sessions does a Cisco router support?

Accepted Answer

Introduction / Context: Remote CLI access to Cisco routers and switches is provided via virtual terminal (VTY) lines. Knowing the default number of VTY lines helps plan concurrent administrative access and configure AAA, access-class filters, and transport settings. Given Data / Assumptions: Default IOS configurations typically create VTY lines 0 through 4. Each VTY line can service one active remote session (Telnet or SSH). Platforms may allow adding more VTYs, but defaults matter for exams and baselines. Concept / Approach: If VTY lines are numbered 0,1,2,3,4, that yields five concurrent sessions. Administrators can view this with show running-config which lists a line vty 0 4 stanza by default. Step-by-Step Solution: Count inclusive range 0–4 => 5 lines.Each line supports one remote connection => 5 simultaneous sessions.Additional VTYs (e.g., 0 15) can be configured if needed on many platforms. Verification / Alternative check: Issue show line or show users to verify active lines and sessions. Config guides show the default block as 0 4. Why Other Options Are Wrong: 2, 3, 4: underestimate default capacity. 16: corresponds to a common custom configuration (0 15) but is not the default. Common Pitfalls: Confusing console/aux lines with VTY lines; forgetting to secure all VTYs with passwords or AAA, leaving some lines open. Final Answer: 5

Question 2

Cisco IOS security basics: Which exact command correctly sets the encrypted enable secret to the value Cisco?

Accepted Answer

Introduction / Context: Privilege escalation in Cisco IOS uses an “enable” password or, preferably, an “enable secret” which is stored as a one-way hash. Using the correct command syntax is critical to secure privileged EXEC access. Given Data / Assumptions: We want to set the secure enable secret value to the literal string “Cisco”. Commands are entered in global configuration mode. Case matters for the configured secret value. Concept / Approach: enable secret sets the hashed secret used when entering privileged EXEC mode. The older enable password stores a weakly encoded or cleartext value (unless type 5/9 via new syntax), so best practice is to use the “secret.” The keyword “password” does not appear in the correct command. Step-by-Step Solution: Enter global config: configure terminal.Apply: enable secret CiscoVerify: show running-config (secret appears as a hash, not cleartext). Verification / Alternative check: Attempting enable from user EXEC prompts for the secret; entering “Cisco” should succeed. The enable password is ignored if an enable secret is configured. Why Other Options Are Wrong: “enable secret password Cisco” contains an invalid extra keyword. “enable secret cisco” sets a different value (lowercase) and does not match the requested literal. “enable password Cisco” configures the weaker legacy mechanism. “service password-encryption Cisco” is a service toggle, not a way to set the secret. Common Pitfalls: Mismatched case; believing service password-encryption secures the enable password to the same standard as the secret; forgetting to save with write memory or copy run start. Final Answer: enable secret Cisco

Question 3

Cisco initial configuration dialog: During the interactive setup dialog, which keystroke immediately terminates (aborts) setup mode and returns you to the CLI?

Accepted Answer

Introduction / Context: Cisco devices may launch the initial configuration dialog (setup mode) when no startup configuration is present. Administrators often need to abort this guided process to enter the normal command line and configure the device manually. Given Data / Assumptions: Question refers to the interactive setup script, not general configuration mode. We need the keystroke that cancels the dialog immediately. Common control sequences have different meanings in IOS contexts. Concept / Approach: Within the setup dialog, pressing Ctrl+C aborts the script and returns the user to the CLI prompt without completing the questionnaire. Other control sequences are used in different modes (e.g., Ctrl+Z ends configuration submodes to privileged EXEC). Step-by-Step Solution: Start the setup dialog (if presented after boot).Press Ctrl+C to abort immediately.Proceed to configure manually with global configuration commands as needed. Verification / Alternative check: After pressing Ctrl+C, the device should present the normal CLI prompt (Router> or Router#) depending on mode, confirming the abort. Why Other Options Are Wrong: Ctrl+Z exits configuration submodes to privileged EXEC, not the setup script. Ctrl+^ and Ctrl+Shift+^ are not standard abort sequences in this context. Esc does not cancel the entire dialog. Common Pitfalls: Confusing Ctrl+Z with abort; attempting to use break sequences that are platform-specific; not saving configuration after manual setup. Final Answer: Ctrl+C

Question 4

Cisco boot behavior: If you erase (delete) the startup configuration in NVRAM and then reboot the router, which mode will the device enter?

Accepted Answer

Introduction / Context: Understanding Cisco IOS boot behavior is key when recovering devices or staging new configurations. The presence or absence of a startup configuration in NVRAM determines whether the interactive setup dialog is presented after boot. Given Data / Assumptions: NVRAM holds the startup configuration file (startup-config). We have deleted this file (e.g., write erase or erase startup-config). The device otherwise boots normally (IOS image is valid). Concept / Approach: When no startup configuration exists, IOS prompts the user with the initial configuration dialog (setup mode) to help create a basic configuration. This is distinct from ROMMON (used when the image or boot variables are missing or corrupt) and distinct from normal EXEC modes that require a configuration to exist. Step-by-Step Solution: Erase startup configuration.Reload the router.Observe: the device enters the setup dialog; you can accept it or press Ctrl+C to abort and configure manually. Verification / Alternative check: Boot logs will show “System configuration dialog” prompt after reload. Creating and saving a new configuration prevents future prompts. Why Other Options Are Wrong: Privileged EXEC and Global configuration modes are not entered automatically without a configuration. “NVRAM loaded mode” is not an IOS concept. ROMMON appears when the system cannot find/boot a valid IOS image, not when the startup-config is missing. Common Pitfalls: Confusing missing startup-config with image boot failure; forgetting to save the running configuration to NVRAM to avoid seeing setup mode in the future. Final Answer: Setup mode (initial configuration dialog)

Question 5

Cisco IOS security behavior You configured a console password, but when you display the running configuration the password is not shown in clear text; it appears obfuscated, for example: Line console 0 Exec-timeout 1 44 Password 7098C0BQR Login What…

Accepted Answer

Introduction / Context: On Cisco IOS devices, plaintext passwords configured under lines (console, vty, aux) or for simple user accounts can be protected from casual viewing in the running-config and startup-config. Understanding which IOS command performs this obfuscation is a core skill for network administrators who audit configurations or harden device security. Given Data / Assumptions: A line password was configured for the console line. The configuration display shows an encoded string instead of the original password (for example, 7098C0BQR). No special AAA server or external encryption is in use; we focus on native IOS behavior. Concept / Approach: The global configuration command service password-encryption turns on a weak, reversible encoding (historically called type 7) that scrambles simple passwords so they do not appear in clear text in configuration files. This is not strong cryptography; it is mainly meant to deter shoulder-surfing and casual disclosure. In contrast, the enable secret command uses a much stronger, hashed representation (for example, type 5 or type 8/9 on newer IOS) but only for the enable password, not for line passwords. Step-by-Step Solution: Recognize that a line password appears encoded in the config (nonsensical characters).Recall that service password-encryption scrambles simple passwords for display.Confirm that exec-timeout affects idle timeouts and does not change password display.Conclude the obfuscation is due to enabling service password-encryption. Verification / Alternative check: If you remove the command and re-enter the same password, the configuration would show it in clear text. Re-enabling the command re-scrambles it. This demonstrates the feature's effect on stored display output. Why Other Options Are Wrong: encrypt password: not a valid IOS global command. service-password-encryption: incorrect syntax (hyphenated form is not used). exec-timeout 1 35: controls idle timeout, not password storage. enable secret: hashes the enable password only; it does not control line password display. Common Pitfalls: Assuming the encoding is strong encryption; it is easily reversible and should not be relied upon for true secrecy. Forgetting to secure configuration files because the passwords look scrambled; treat configs as sensitive data. Final Answer: service password-encryption

Question 6

Clearing saved configuration On a Cisco router, which command deletes the contents of NVRAM by erasing the saved startup configuration so the device boots with a default configuration on the next reload?

Accepted Answer

Introduction / Context: NVRAM stores the startup configuration that a Cisco router loads during boot. When you need to factory-reset the device's saved configuration (for lab work, decommissioning, or troubleshooting), you erase the startup-config stored in NVRAM. Knowing the correct command and its common abbreviations prevents accidental data loss or confusion about what configuration file you are modifying. Given Data / Assumptions: The goal is to remove the saved configuration in NVRAM (startup-config), not the running-config in RAM. We are using classic IOS CLI where command abbreviations are accepted. A reload after erasing is typically required to take effect cleanly. Concept / Approach: The canonical command is often entered as erase startup-config. IOS supports unambiguous abbreviations, so erase start is commonly used and accomplishes the same task. Alternative historical forms include write erase on many platforms, which also erases the startup-config. After erasing, reloading the router causes it to start with the default, unconfigured state. Step-by-Step Solution: Enter privileged EXEC mode.Execute: erase start (an abbreviation for erase startup-config).Confirm the prompt to erase NVRAM contents.Reload the device to boot without the previous configuration. Verification / Alternative check: Running show startup-config before and after confirms that NVRAM has been cleared. Upon reload, the initial setup dialog appears, confirming the absence of a saved configuration. Why Other Options Are Wrong: delete NVRAM / erase NVRAM: not standard, platform-independent IOS commands. delete startup-config: on some platforms it may work, but the standard lab-proven method is erase startup-config; the question expects that form or its abbreviation. write erase: is valid on many systems but is not among the choices marked correct here; the provided correct equivalent is erase start. Common Pitfalls: Confusing running-config with startup-config; erasing NVRAM does not immediately change the running configuration until reload. Forgetting to save a backup before erasing if the config is needed later. Final Answer: erase start

Question 7

Interface status interpretation After issuing show interface serial 0, you see: “Serial0 is administratively down, line protocol is down.” What does this indicate about the interface state?

Accepted Answer

Introduction / Context: Cisco IOS interface status messages help quickly diagnose whether a problem is due to configuration, physical cabling, or protocol negotiation. Understanding the difference between “administratively down” and “down” saves time during triage and points to the right corrective action. Given Data / Assumptions: The interface output states “administratively down, line protocol is down.” No additional error messages are given. We assume standard IOS behavior and terminology. Concept / Approach: “Administratively down” means the interface has been disabled via configuration, typically with the shutdown command under the interface. Because the interface is disabled, the line protocol is also down. This is distinct from an interface that is physically down due to cabling or clocking problems, which would show “Serial0 is down, line protocol is down.” Step-by-Step Solution: Read the first status: “administratively down.”Map this to a configured shutdown state.Infer the cause: the interface has been intentionally disabled by an administrator.Resolution: enter interface configuration mode and issue no shutdown to enable it. Verification / Alternative check: After issuing no shutdown, the first status should change to “up” if the physical layer is good; line protocol will then attempt to come up depending on encapsulation and keepalives. Why Other Options Are Wrong: Mismatched keepalives, missing cable, or PPP failures cause “down/down” or “up/down,” not “administratively down.” Pinging from the interface does not toggle administrative state. Common Pitfalls: Confusing “administratively down” with “down” and troubleshooting cabling when the fix is simply no shutdown. Final Answer: The administrator has manually shut down the interface.

Question 8

Login messages on Cisco IOS You want administrators to see a custom login message before they access the router. Which IOS command creates this message banner of the day?

Accepted Answer

Introduction / Context: Displaying a legal notice or operational reminder at login is a common security and compliance practice on network devices. Cisco IOS supports several banners, including message of the day (MOTD), login, and exec banners. The most frequently used for general pre-login notices is the MOTD banner. Given Data / Assumptions: Administrators connect via console, SSH, or Telnet. We want a message to appear before authentication prompts. We are using classic IOS syntax in global configuration mode. Concept / Approach: The command banner motd defines a message of the day banner. After typing the command, IOS prompts for a delimiting character, then you type the banner text, and end with the same delimiter. The MOTD banner is displayed to all users before they log in, making it suitable for legal disclaimers and system-wide announcements. Step-by-Step Solution: Enter global configuration mode.Type: banner motd #Enter your message lines and close with the delimiter #Verify by initiating a new login session to see the banner. Verification / Alternative check: You can also configure banner login to display a message immediately before the username/password prompt; however, the exam-standard choice for general pre-login messaging is the MOTD banner. Why Other Options Are Wrong: message banner motd / banner message motd / message motd: invalid IOS command formats. banner login motd: mixes two different banner types; not valid syntax. Common Pitfalls: Forgetting to terminate the banner text with the chosen delimiter, leaving the terminal stuck in banner input mode. Using special characters in the banner that may be interpreted by terminals; test the banner in your environment. Final Answer: banner motd

Question 9

Layer diagnosis from interface status You issue show interface serial 1 and see: “Serial1 is down, line protocol is down.” Which OSI layer is most likely where the fault resides?

Accepted Answer

Introduction / Context: Cisco IOS provides two key indicators per interface: the physical interface status and the line protocol status. These map closely to OSI Layer 1 (Physical) and Layer 2 (Data Link). Being able to infer the likely fault domain from the combined status accelerates troubleshooting of WAN serial links and Ethernet ports alike. Given Data / Assumptions: Status shown is “down/down” (both the interface and the line protocol are down). No “administratively” qualifier is present. We are working with standard encapsulations and defaults. Concept / Approach: “Down/down” often indicates a Layer 1 problem: bad or disconnected cable, wrong CSU/DSU settings, no clocking on DCE, or hardware failure. When Layer 1 is down, the Layer 2 protocol cannot come up, hence both states are down. By contrast, “up/down” points to a Layer 2 mismatch (encapsulation, keepalives), and “administratively down” signals a configured shutdown. Step-by-Step Solution: Read the physical status: down.Read the line protocol status: down.Map “down/down” to likely Layer 1 issues (cabling, clocking, hardware).Investigate physical connections and clock rate before L2/L3 settings. Verification / Alternative check: Use show controllers serial to verify DTE/DCE state and clocking, check cabling, and consult CSU/DSU LEDs to confirm signal presence. Why Other Options Are Wrong: Data Link or Network layers: would typically present as “up/down” or routing issues with “up/up.” Router software problem: not indicated by this specific status pair. Transport layer: unrelated to interface link states. Common Pitfalls: Jumping to reconfigure encapsulation when the cable is simply unplugged. Ignoring DCE/DTE roles and missing clock rate on lab serial connections. Final Answer: Physical layer

Question 10

Decoding IOS error prompts You typed Router# show serial 0/0 and received: ^ % Invalid input detected at '^' marker Why did IOS display this error?

Accepted Answer

Introduction / Context: The Cisco IOS parser provides caret (^) error feedback to indicate where it stopped understanding the command. Reading that position and recalling correct command syntax lets you correct mistakes quickly without guesswork. This is especially useful for similar commands that share prefixes, such as show interface, show ip interface, and show controllers. Given Data / Assumptions: Command entered: show serial 0/0. IOS responded with an “Invalid input” error with the caret under the word “show” or immediately after it, highlighting the unexpected token. You are already at the privileged prompt (Router#), so privilege is not the problem. Concept / Approach: The correct command to display interface status is show interface serial 0/0 (or the accepted abbreviation show int s0/0). The keyword interface is required. Without it, IOS does not recognize “show serial …” as a valid top-level command, so it flags the error at the point where parsing fails. Step-by-Step Solution: Recall the standard structure: show interface .Re-enter the command: show interface serial 0/0.Optionally, use shorthand: show int s0/0.Verify output now shows line status, protocol status, and counters. Verification / Alternative check: Use context-sensitive help: typing show ? reveals available subcommands; show interface ? then lists interface types and names. This confirms the correct syntax. Why Other Options Are Wrong: Privilege mode: you are already at Router#, so privilege is sufficient. Spacing: IOS allows spaces; spacing is required between tokens. No such interface: while possible, the specific syntax error occurs before IOS checks existence. Terminal type: unrelated to command parsing. Common Pitfalls: Forgetting middle keywords such as interface, ip, or frame-relay. Misreading the caret position and troubleshooting the wrong part of the command. Final Answer: Part of the command is missing; use show interface serial 0/0.

Question 11

Identifying DTE vs. DCE cabling Which Cisco IOS command reveals whether a DTE or DCE cable is connected to Serial0 and shows associated controller information?

Accepted Answer

Introduction / Context: In lab environments and some WAN setups, one side of a serial link provides clocking (DCE) while the other is DTE. Determining which side is DCE is essential because the DCE end must be configured with a clock rate for the link to function. Cisco IOS provides controller-level commands to view this hardware-level detail. Given Data / Assumptions: We are working with classic serial interfaces (for example, Serial0). We need to know whether the attached cable is DTE or DCE. We want a command that surfaces controller information beyond high-level interface status. Concept / Approach: The command show controllers serial 0 displays hardware and controller information for the serial interface, including whether the interface detects a DTE or DCE cable. If DCE is present, you typically must set a clock rate on that interface. High-level commands like show interface will not reliably show the cable role. Step-by-Step Solution: Enter privileged EXEC mode.Execute: show controllers serial 0.Look for output lines stating DTE or DCE.If DCE, configure an appropriate clock rate on the interface. Verification / Alternative check: You can also check both ends of the link; only one side should show DCE. On the DCE side, clock rate is required for lab back-to-back cables. Why Other Options Are Wrong: show interface s0 / show interface serial 0: useful for L1/L2 status but not definitive for cable type. show serial 0 controllers: invalid syntax for IOS. show cable-type serial 0: not an IOS command. Common Pitfalls: Setting clock rate on the DTE side and wondering why the link remains down. Relying on interface status alone without controller details. Final Answer: show controllers serial 0

Question 12

Finding interface IP and link status Which set of IOS commands will display an interface’s current IP addressing and its Layer 1/Layer 2 status information?

Accepted Answer

Introduction / Context: Troubleshooting an IOS interface usually begins by confirming the IP address and the basic link state at Layer 1 (physical) and Layer 2 (data link). Multiple IOS commands expose these details from different angles. Knowing which commands provide what information helps you build a quick, repeatable triage flow. Given Data / Assumptions: The candidate commands are: show version; show protocols; show interfaces; show controllers; show ip interface. We need to see IP addressing and link state (L1/L2). Standard IOS behavior is assumed. Concept / Approach: show protocols lists the routed protocols and shows, per interface, whether they are up along with configured IP addresses. show interfaces provides comprehensive per-interface information including line status (up/down), protocol state, errors, and the interface's IP address. show ip interface summarizes IP-specific details (address, helper settings, ACLs) and includes interface status. In contrast, show version focuses on platform information and software, and show controllers provides low-level hardware/controller diagnostics without consistently listing IP addressing. Step-by-Step Solution: Use show protocols to confirm configured IP and basic up/down state.Use show interfaces to view L1/L2 status, errors, and the IP line in the output.Use show ip interface to confirm L3 details and operational status.Correlate the outputs to diagnose both addressing and link problems. Verification / Alternative check: Cross-checking across these three commands ensures accuracy: mismatches often reveal misconfigurations such as shutdown interfaces with IPs configured or ACLs blocking traffic despite link status being up. Why Other Options Are Wrong: Option A: show version does not list interface IPs; show controllers lacks full IP context. Option C: omits show protocols or show ip interface, both of which help confirm IP addressing. Option D: incorrect because a correct set exists. Option E: show version again doesn't show interface IPs. Common Pitfalls: Using only one command and missing a key clue (for example, L1 up but L2 down). Misreading cached outputs; always refresh with a new command invocation. Final Answer: 2, 3 and 5 (show protocols; show interfaces; show ip interface)

Question 13

Restoring startup configuration You want to completely reinitialize the router so that the current running configuration is replaced by the saved startup configuration. Which command accomplishes this?

Accepted Answer

Introduction / Context: Routers maintain two primary configuration states: the running-config in RAM and the startup-config in NVRAM. To make the device apply the saved startup configuration in a clean state, you must reload the device so it boots fresh and reads startup-config at initialization. This is different from simply merging configurations while the device is running. Given Data / Assumptions: The goal is to reinitialize the router (cold start of processes). We want the running-config to be replaced by the startup-config after reboot. We are not trying to save changes to NVRAM first. Concept / Approach: The command reload restarts the router. During boot, IOS loads the startup-config from NVRAM into RAM, which becomes the new running-config. By contrast, copy start run merges the startup-config into the existing running configuration without clearing the current state, which can leave residual settings. copy run start saves the current configuration, which is the opposite of what we want. Step-by-Step Solution: Verify that the desired startup-config is present (show startup-config).Issue reload and confirm the reboot.After boot, validate that running-config reflects the saved startup-config.If needed, erase start first to reinitialize to factory defaults, then reload. Verification / Alternative check: Post-reload, show running-config should match show startup-config taken before the reload, confirming that the startup-config has been applied cleanly. Why Other Options Are Wrong: replace run start: not a standard IOS command. copy run start: saves current RAM config to NVRAM; does not reinitialize. copy start run: merges configurations and can leave stale settings. restart-config: not an IOS command. Common Pitfalls: Expecting copy start run to “replace” the configuration; it merges and may cause unexpected composite configs. Reloading without confirming the startup-config, leading to surprises after reboot. Final Answer: reload

Question 14

Understanding exec-timeout values You run show running-config and see: Line console 0 Exec-timeout 1 35 Password CURIOUSTABPASSWD Login What do the two numbers following exec-timeout indicate for the console line?

Accepted Answer

Introduction / Context: The exec-timeout setting on Cisco IOS line configurations determines how long an EXEC session can remain idle before the device disconnects it. This helps enforce security hygiene and frees resources on busy devices. The command uses a two-parameter format that frequently confuses newcomers. Given Data / Assumptions: The configuration shows exec-timeout 1 35 on the console line. The numbers represent minutes and seconds, respectively. We focus on local console behavior, not vty-specific differences. Concept / Approach: The syntax is exec-timeout . Therefore, exec-timeout 1 35 means 1 minute and 35 seconds of inactivity (no keystrokes entered) will cause the console session to terminate. A value of 0 0 disables the timeout (no automatic disconnect). The setting applies to the specific line context where it is configured (console, aux, or vty). Step-by-Step Solution: Parse the two numbers as minutes and seconds.Map 1 and 35 to 1 minute and 35 seconds.Conclude that idle console sessions will be disconnected after that period with no input.Recognize that output activity alone does not reset the timer; user input is required. Verification / Alternative check: Testing by leaving the console idle for 95 seconds (1 minute 35 seconds) results in IOS closing the session and returning to the password prompt on the next key press, confirming the configuration behavior. Why Other Options Are Wrong: 35 seconds only: ignores the minutes parameter. 1 hour and 35 minutes: misreads units; the first number is minutes, not hours. Telnet-only behavior: exec-timeout applies to whichever line it is set on; here it is the console. 96 seconds claim: mathematically off (1*60 + 35 = 95 seconds), and the definition requires user input inactivity. Common Pitfalls: Assuming device output resets the timer; typically only user input does. Forgetting to set an appropriate timeout on vty lines, leaving remote sessions open indefinitely. Final Answer: If no commands are typed in 1 minute and 35 seconds, the console connection will be closed.

Question 15

Cisco IOS configuration modes and VTY lines: On a Cisco router, which command (typed in the correct configuration mode) configures all of the default virtual terminal (VTY) lines used for Telnet/SSH access (lines 0 through 4)?

Accepted Answer

Introduction / Context: Virtual terminal (VTY) lines on Cisco IOS devices are used for remote administrative sessions such as Telnet or Secure Shell (SSH). Knowing how to enter the correct configuration submode to apply passwords, login methods, and transport protocols to all default VTY lines (0–4) is essential for secure router access control. Given Data / Assumptions: The device is a Cisco router running IOS. We want to configure the default set of VTY lines, which are 5 lines numbered 0 through 4. Commands must be entered from the correct mode hierarchy: user EXEC → privileged EXEC → global configuration → line configuration. Concept / Approach: To configure multiple VTY lines at once, you enter global configuration mode and then the line submode for the range. The canonical syntax is line vty 0 4 from Router(config)#. Inside that submode you can set password, login, transport input ssh, and apply access-class filters. Step-by-Step Solution: From privileged EXEC, type: configure terminalEnter the VTY line range: line vty 0 4Apply desired settings: password, login local, transport input ssh, etc.Exit and save: end, then copy running-config startup-config Verification / Alternative check: Use show running-config | section line vty to confirm that the configuration applied to lines 0–4. Attempt a Telnet/SSH session to validate access behavior matches policy. Why Other Options Are Wrong: Router#line vty 0 4 shows the wrong prompt; you must be in global config, not user/privileged EXEC. Router(config-if)#line console 0 configures the console line, not VTY. Router(config)#line vty all is not valid IOS syntax; specify the numeric range. Common Pitfalls: Forgetting to include the entire range (0–4), leaving some lines unprotected; configuring Telnet without SSH; omitting login or AAA, which can lock out access or weaken security. Final Answer: Router(config)#line vty 0 4

Question 16

Comprehensive interface status review: Which Cisco IOS command displays the configurable parameters and runtime statistics for all router interfaces (physical and logical)?

Accepted Answer

Introduction / Context: Troubleshooting connectivity requires visibility into interface health and configuration. Cisco IOS provides several show commands, but only one gives a full, consolidated report of operational statistics, errors, encapsulation, bandwidth, duplex, and IP details for all interfaces. Given Data / Assumptions: You need both configuration-related information and live counters in a single output. Multiple interface types may exist (Ethernet, Serial, Loopback, VLAN SVI). The goal is to examine status, not merely the saved or current config text. Concept / Approach: The command show interfaces prints per-interface blocks showing line protocol state, hardware address, MTU, BW, delay, reliability, load, encapsulation, input/output rate, errors, drops, and IP details. It is the broadest, statistics-rich view across all interfaces. Step-by-Step Solution: Enter privileged EXEC (Router#).Run: show interfacesOptionally filter: show interfaces | include errors | dropCorrelate with: show ip interface brief for concise up/down and addressing. Verification / Alternative check: Compare with show running-config: it shows config lines but not live counters and errors. show interfaces provides packet statistics and error counters that confirm physical or data-link problems. Why Other Options Are Wrong: show running-config and show startup-config display configuration text only. show versions is not a standard command; the common one is show version for software/hardware inventory, not per-interface stats. Common Pitfalls: Relying solely on show ip interface brief and missing duplex mismatches or CRC errors; overlooking interface resets and input errors that indicate cabling or speed/duplex issues. Final Answer: show interfaces

Question 17

Saving configuration to NVRAM: Which exact Cisco IOS command (entered from privileged EXEC) saves the current running configuration in RAM to the startup configuration in NVRAM?

Accepted Answer

Introduction / Context: On Cisco IOS, configuration changes are made to the running configuration in RAM. To ensure those changes persist across reloads, you must copy the running configuration to the startup configuration stored in NVRAM. Recognizing the correct command and mode prevents accidental loss of settings after a reboot. Given Data / Assumptions: We are working on a Cisco router. The goal is to save the running configuration so it is retained after a reload. The question emphasizes the proper command and prompt context. Concept / Approach: Persistence is achieved with the IOS copy command. In privileged EXEC mode (Router#), the canonical long form is copy running-config startup-config. IOS also permits supported abbreviations, commonly written as copy run startup, which is functionally identical. The operation writes the configuration snapshot into NVRAM for the next boot. Step-by-Step Solution: Enter privileged EXEC: enableExecute: copy run startupConfirm prompts as needed; verify with: show startup-configOptionally archive to external storage: copy run tftp Verification / Alternative check: Reload the router (or issue show startup-config) to confirm the saved configuration matches the intended changes. The running and startup configurations should align after a successful copy. Why Other Options Are Wrong: Option A is not valid IOS syntax. Option B reverses the direction (that would overwrite the running config from startup, not save changes). Option C shows the long form but at the wrong prompt (Router(config)#); the command is not executed from global configuration mode. Common Pitfalls: Forgetting to save after changes; misreading the direction of copy; assuming write memory happens automatically (on modern IOS you can use write memory, but it must still be invoked). Final Answer: Router#copy run startup

Question 18

Understanding IOS command parsing: At the privileged EXEC prompt, you type the abbreviated command “sh ru” and receive “% ambiguous command” in response. What is the reason for this message?

Accepted Answer

Introduction / Context: Cisco IOS allows command abbreviation so long as the typed prefix uniquely identifies a single command. When an abbreviation matches multiple possible commands, IOS cannot decide which one you intend and returns an ambiguity error. Understanding this behavior helps you create reliable shorthand and diagnose parser complaints quickly. Given Data / Assumptions: You typed sh ru at the Router# prompt. The IOS parser compares your input against the command tree under show. At least two show subcommands begin with ru. Concept / Approach: Abbreviations work only if they are unambiguous. If both show running-config and another command such as show rusers or platform-specific variants exist, the prefix ru matches more than one candidate, triggering the “% ambiguous command” message. You must either type more characters (e.g., show run) or the full command. Step-by-Step Solution: Repeat the command with additional characters: show runIf still ambiguous, press ? after show r to list valid continuations.Use command history and context to avoid ambiguity in future entries. Verification / Alternative check: Type show ru? to see the parser’s options; the list will contain multiple entries starting with ru, confirming ambiguity. Why Other Options Are Wrong: Lacking parameters (A) is different from ambiguity; many show commands can run without extra parameters. Claiming no command starts with ru (C) is false; running-config clearly does. Wrong mode (D) is not the issue—show commands are valid at privileged EXEC. Common Pitfalls: Over-abbreviating on different IOS versions where command sets vary; relying on an alias from one platform that does not exist on another, causing unexpected ambiguity. Final Answer: There is more than one show command that starts with the letters ru.

Question 19

Finding a LAN’s broadcast address from user EXEC: From user mode on a Cisco router, which command will display the broadcast address used on a connected LAN interface along with other interface details?

Accepted Answer

Introduction / Context: When validating IP addressing on a LAN, you may need to confirm the broadcast address computed from the interface’s IP and mask. IOS includes this information in the detailed interface output. Selecting the right show command ensures you see the operational parameters and layer-3 details for the interface in question. Given Data / Assumptions: We are at user EXEC mode (Router>), where many show commands are allowed. We want to view a field explicitly showing the broadcast address. We need per-interface operational details, not just configuration lines. Concept / Approach: show interfaces displays a comprehensive block per interface that includes IP address, subnet mask, and the derived broadcast address. While show protocols summarizes IP addressing state, the detailed broadcast line consistently appears in the interface-specific output, making show interfaces the most reliable choice for this task. Step-by-Step Solution: From Router>, type: show interfacesScroll to the target LAN interface (e.g., FastEthernet0/0).Locate the line indicating IP address, mask, and broadcast address.Optionally refine: show interface FastEthernet0/0 for a single port. Verification / Alternative check: Compute the broadcast address manually from IP/mask and confirm it matches the value reported by IOS, ensuring correctness of the configured subnet. Why Other Options Are Wrong: show running-config and show startup-config list configuration but often omit computed broadcast fields. show protocols offers a brief summary and may not display the broadcast address as explicitly as show interfaces. Common Pitfalls: Confusing user EXEC versus privileged EXEC availability; neglecting to check the specific interface when multiple LANs exist; relying on outdated cached values after recent changes—always verify live output. Final Answer: show interfaces

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