Answers and Explanations
A1: Answer: C. The Cisco Discovery Protocol is proprietary to Cisco and can give an administrator's address and other information regarding directly connected devices. A is incorrect, as UDP is a fast, connectionless, and nonproprietary protocol. B is incorrect, as TCP is a nonproprietary, connection-oriented, and reliable protocol used in network communication. D is incorrect because SNMP is used for network management and is not proprietary to Cisco.

A2: Answer: B. CDP runs at the Data-link layer, allowing it to be network layer protocol-independent, working with both IP- and IPX-based networks. A is incorrect, as CDP does not operate at the Physical layer, and D is incorrect because CDP does not operate at the Transport layer. C is incorrect because IP and IPX are network-based protocols, but CDP is not.

A3: Answers: A, B, C, E, and F. CDP can provide the device hardware platform, a list of supported features such as source-route bridge, the network layer address, IOS version, and a device identifier such as the device's hostname. D is incorrect as CDP doesn't display open ports on the neighboring device.

A4: Answer: A. CDP is enabled by default. B and C are incorrect because even though CDP can be controlled in Global Configuration mode, it is enabled by default. D is incorrect because CDP can be turned on or off as necessary.

A5: Answer: D. You must enter the cdp run command from Global Configuration mode. A is incorrect because the cdp enable command is used in interface configuration mode and enables CDP on a particular interface. B is incorrect because the cdp enable command does not work in Global Configuration mode. C is incorrect; the command is right but must be in Global Configuration mode, not Interface Configuration mode.

A6: Answer: B. The proper syntax on Cisco routers is no cdp run. A is incorrect; cdp disable is not a valid command. C is incorrect; the syntax is proper for older Catalyst Switches only, and is not valid today. D is incorrect; this is an invalid command resulting in an error message.

A7: Answer: A. Telnet can be used to gather information about remote devices. B is incorrect; FTP is used to transfer files and can include authentication. C is incorrect; TFTP uses no authentication. D is incorrect, as CDP can gather information about neighboring devices only. If you telnet to a remote device, CDP may show information about the remote device's neighbors. However, without Telnet, CDP has no capability to display remote device information.

A8: Answer: A, B, and C. Each of these commands attempts a Telnet session with Router1. D is incorrect, as you want to telnet to Router1, not Router2.

A9: Answer: C. The show sessions command verifies your Telnet connectivity and displays a list of hosts to which you have established a connection. A and B are incorrect because they are not valid IOS commands. D is incorrect; the show users command displays remote users who have initiated a session to your router.

A10: Answer: D. The show users command displays remote users who have initiated a session to your router. A and B are not valid IOS commands. C is incorrect; show sessions verifies your Telnet connectivity and displays a list of hosts to which you have established a connection.

A11: Answer: D. The asterisk indicates your last session in the show session's output. A is incorrect; this symbol is most closely associated with Privileged EXEC mode. B is incorrect; this symbol does not indicate the most recent session. C is incorrect; the caret indicates where an error begins in a mistyped command.

A12: Answer: C. Simply pressing Enter resumes the last session. A is incorrect; pressing Tab completes partially entered commands. B and D are incorrect; these sequences do not perform the desired function.

A13: Answer: A. The correct key sequence to perform this task is Ctrl+Shift+6, followed by pressing x. B, C, and D are incorrect, as all other key sequences do not perform the correct task.

A14: Answers: A, B, and C. These are all valid ways to continue a suspended session. D is incorrect; continue session is not a valid IOS command.

A15: Answer: A. The clear line command, accompanied by the line number, clears the session. B is incorrect; this syntax is not supported. C and D are invalid IOS commands.

A16: Answer: A. ping uses ICMP and generates information regarding connectivity to the remote host. B is incorrect; although trace can determine connectivity, it generates more traffic than ping. C is incorrect; telnetting to the remote host can confirm connectivity, but it generates more traffic to do so. D is incorrect; tftp cannot be used to test connectivity to a remote router.

A17: Answer: B. TRace can determine connectivity, and it shows the path the traffic takes to the destination. A is incorrect, as ping uses ICMP and generates information regarding connectivity to the remote host but does not show the path. C is incorrect because telnetting to the remote host can confirm connectivity, but it doesn't provide path information. D is incorrect because tftp cannot be used to test connectivity to a remote router; it is used for transferring files.

A18: Answer: A. RAM contains the software and data structures that allow the router to function, so A is the correct response. IOS and the running configuration are part of RAM. B is incorrect, as ROM contains the microcode for functions such as bootstrap and POST, and also contains ROMMON. C is incorrect; flash memory contains the Cisco IOS software image and is nonvolatile. D is incorrect because NVRAM is nonvolatile and is used to store the startup-config. E is incorrect; the configuration register controls how the router boots up.

A19: Answer: B. ROM contains the microcode for functions such as bootstrap and POST, and also contains ROMMON. A is incorrect because RAM contains the software and data structures that allow the router to function. IOS and the running configuration are part of RAM. C is incorrect; Flash memory contains the Cisco IOS software image and is nonvolatile. D is incorrect, as NVRAM is nonvolatile and is used to store the startup-config. E is incorrect because the configuration register controls how the router boots up.

A20: Answer: C. Flash memory contains the Cisco IOS software image and is nonvolatile. A is incorrect because RAM contains the software and data structures that allow the router to function, and IOS and the running configuration are part of RAM. B is incorrect; ROM contains the microcode for functions such as bootstrap and POST, and also contains ROMMON. D is incorrect because while NVRAM is nonvolatile, it is used to store the startup-config, not the IOS software image itself. E is incorrect; the configuration register controls how the router boots up.

A21: Answer: D. NVRAM is nonvolatile and is used to store the startup-config. A is incorrect, as RAM contains the software and data structures that allow the router to function, and IOS and the running configuration are part of RAM. B is incorrect because ROM contains the microcode for functions such as bootstrap and POST, and also contains ROMMON. C is incorrect because flash memory contains the Cisco IOS software image and is nonvolatile. E is incorrect; the configuration register controls how the router boots up.

A22: Answer: D. The configuration register controls how the router boots up, so D is the correct answer. A is incorrect, as RAM contains the software and data structures that allow the router to function, and IOS and the running configuration are part of RAM. B is incorrect because ROM contains the microcode for functions such as bootstrap and POST, and also contains ROMMON. C is incorrect; Flash memory contains the Cisco IOS software image and is nonvolatile.

A23: Answer: B. ROMMON is a low-level operating system used for password recovery and troubleshooting; it has no routing or IP capabilities. A is incorrect; bootstrap code is used to bring the router up during initialization and to read the configuration register to determine how to boot. C is incorrect; POST is the microcode used to determine the router's hardware configuration. D isincorrect, as the mini-IOS software file is a subset of the Cisco IOS for loading a new IOS image into flash and performing other maintenance operations.

A24: Answer: C. POST is the microcode used to determine the router's hardware configuration. A is incorrect because bootstrap code is used to bring the router up during initialization and to read the configuration register to determine how to boot. B is incorrect; ROMMON is a low-level operating system used for password recovery and troubleshooting, and it has no routing or IP capabilities. D is incorrect because the mini-IOS software file is a subset of the Cisco IOS for loading a new IOS image into flash and performing other maintenance operations.

A25: Answer: A. Bootstrap code is used to bring the router up during initialization and to read the configuration register to determine how to boot. B is incorrect because POST is the microcode used to determine the router's hardware configuration. C is incorrect, as ROMMON is a low-level operating system used for password recovery and troubleshooting; it has no routing or IP capabilities. D is incorrect, as the mini-IOS software file is a subset of the Cisco IOS for loading a new IOS image into flash and performing other maintenance operations.

A26: Answer: D. The mini-IOS software file is a subset of the Cisco IOS for loading a new IOS image into flash and performing other maintenance operations. A is incorrect because bootstrap code is used to bring the router up during initialization and to read the configuration register to determine how to boot. B is incorrect; POST is the microcode used to determine the router's hardware configuration. C is incorrect; ROMMON is a low-level operating system used for password recovery and troubleshooting, and it has no routing or IP capabilities.

A27: Answer: B. The show flash command lists the contents of flash memory, including the IOS image file stored there. A is incorrect; show ios is an invalid command. C is incorrect; ls works in Unix, but it is not a Cisco IOS command. D is incorrect because list flash is not a valid IOS command.

A28: Answer: B. The show running-config command displays the current running configuration of the router, which is kept in RAM. C is incorrect; show startup-config lists the contents of NVRAM and the configuration used on startup. A and D are incorrect because they are invalid IOS commands.

A29: Answer: C. The show startup-config command lists the contents of NVRAM and the configuration used on startup. B is incorrect because show running-config displays the current running configuration of the router, which is kept in RAM. A and D are invalid IOS commands.

A30: Answer: A. A configuration register value of 0x0 in the boot field causes the router to use ROM monitor mode, so A is the correct response. B is incorrect because a configuration register value of 0x1 in the boot field causes the router to automatically boot from ROM. C is incorrect, as a configuration register value of 0x2 in the boot field causes the router to examine NVRAM for boot system commands. D is incorrect because a configuration register value to automatically boot from RAM is not defined.

A31: Answer: B. A configuration register value of 0x1 in the boot field causes the router to automatically boot from ROM. A is incorrect because a configuration register value of 0x0 in the boot field causes the router to use ROM monitor mode. C is incorrect because a configuration register value of 0x2 in the boot field causes the router to examine NVRAM for boot system commands. D is incorrect, as a configuration register value to automatically boot from RAM is not defined.

A32: Answer: C. A configuration register value of 0x2 in the boot field causes the router to examine NVRAM for boot system commands. A is incorrect because a configuration register value of 0x0 in the boot field causes the router to use ROM monitor mode. B is incorrect because a configuration register value of 0x1 in the boot field causes the router to automatically boot from ROM. D is incorrect, as a configuration register value to automatically boot from RAM is not defined.

A33: Answer: D. The show version command displays the configuration register setting. A is incorrect, as show running-config does not display the configuration register. B is incorrect, as the command show startup-config does not display the configuration register value. C is an invalid IOS command.

A34: Answer: C. The config-register command followed by the register setting is the correct syntax to use for setting the configuration register. B is incorrect because this is not the proper syntax to set the configuration register. A and D are not valid IOS commands.

A35: Answers: B and C. The bits of the configuration register can also set the baud rate and have the router use the configuration saved in NVRAM. A is incorrect; the configuration register does not enable IP. D is incorrect; the configuration register cannot enable the AUX port.

A36: Answers: A, B, C, and D. The prefix bootflash: refers to bootflash memory, flh: refers to flash load helper log files, flash: refers to flash memory, and nvram: refers to NVRAM. E and F are incorrect, as ram: and rom: are not valid IFS prefixes.

A37: Answer: B. Special capabilities are represented by the second portion (js). A is incorrect; the platform is represented by the first portion (c2500). C is incorrect; where the image runs is indicated by the third portion ("1"). D is incorrect; the last portion (120-3) is the version number.

A38: Answer: B. CDP stands for Cisco Discovery Protocol, which is used to help manage and monitor Cisco devices. A, B, and D are incorrect, as they are not valid protocols.

A39: Answer: C. The copy flash tftp command copies the contents located in flash to TFTP. A is incorrect, as this merges your starting configuration into your running configuration. B is incorrect; this overwrites your starting configuration with your active, running configuration. D is incorrect, as this copies data from the TFTP server into flash.

A40: Answer: A. The erase startup-config command deletes the information stored in NVRAM. B, C, and D are invalid IOS commands.

A41: Answer: C. The service timestamps command records a time stamp with logged information, so C is the correct response. A, B, and D are invalid IOS commands.

A42: Answer: C. The no debug all command disables all debugging on the router. The other responses are all invalid IOS commands.

A43: Answer: C. The debug all command is extremely resource-intensive and should not be used. A is incorrect; this command can be used, even though it is an older form of copy running-config startup-config. B is incorrect because this command does not cause a system crash; it merges your starting configuration into your running configuration. D is an invalid IOS command.

A44: Answer: B. The show flash command displays the current amount of flash memory installed on the system. A is incorrect; show memory shows detailed information about the RAM on the router. C is incorrect because the startup configuration does not include memory information. D is an invalid IOS command.

A45: Answer: C. The terminal monitor command displays console messages to your Telnet session and is useful for remote troubleshooting. The other responses are all invalid IOS commands.

A46: Answer: C. The show processes command displays information regarding the CPU utilization on the router, so C is correct. If the CPU is heavily taxed, debugging may cause extreme performance degradation. A is incorrect; this command enables time stamps with logging information. B and D are invalid IOS commands.

A47: Answer: A. This command copies the configuration currently in use (running-config) to your TFTP server. B is incorrect; this command copies the starting configuration to your TFTP server. The starting configuration is not the currently running configuration, but the configuration used when the router boots. C is incorrect; this command copies from the TFTP server to the running configuration. D is incorrect, as this command copies from the TFTP server to the starting configuration.

A48: Answer: C. When you copy from any location into RAM, a merge occurs. Nonconflicting settings are kept and added, and conflicting settings are overwritten. A is incorrect; you should perform a backup when making this operation, but one is not performed automatically. B is incorrect; the running configuration is not lost. D is incorrect; no error message is returned.

A49: Answer: B. When you copy the running configuration from RAM into the startup configuration, the startup configuration is lost, replaced by the running configuration. A is incorrect; a backup is created only if you manually create one. C is incorrect; merges occur only when you are copying from anywhere into RAM. D is incorrect, as no error message is returned.

A50: Answer: A. This problem can be fixed in ROMMON mode, and this is the first step you must take. B is incorrect because you must enter ROMMON mode first. C is incorrect; the problem does not lie in RAM, and you must enter ROMMON mode first, regardless. D is incorrect; the problem is not in NVRAM, and you must enter ROMMON mode first.