Cisco 100-490 Exam

The tftpdnld command is specifically designed to initiate a TFTP (Trivial File Transfer Protocol) transfer of an image within ROMmon mode on a Cisco device. Here's why it's the correct answer:

ROMmon Functionality: ROMmon (Read-Only Memory Monitor) is a basic operating system mode used when the main Cisco IOS is unavailable. The tftpdnld command works from ROMmon to download a new IOS image.

TFTP Protocol: The tftpdnld command utilizes TFTP, which is a simple and reliable protocol commonly used for transferring Cisco IOS images.

Purpose: The command is used primarily for recovering corrupt images or upgrading to a different IOS version.

Why other options are incorrect:

Xmodem: XMODEM is an older and less reliable file transfer protocol that's less suitable than TFTP for Cisco IOS image transfers.

copy tftp: flash: This command format is used within the Cisco IOS itself, not in ROMmon mode.

copy flash: tftp: This command format would attempt to upload an image from flash memory to a TFTP server, instead of downloading an image.

1. It is built on a client-server model architecture and uses separate control and data connections between the client and the server2. Here are the explanations for the correct answers:

* B: The copy running-config ftp: command is used to copy the running configuration from a router to an FTP server or vice versa. This is a common method for backing up and restoring configurations on Cisco devices1.

* E: FTP typically requires authentication, which means a Cisco router acting as an FTP client must be configured with the appropriate username and password to access an FTP server. This ensures secure file transfer and access control1.

The other options are incorrect because:

* A: FTP is not used to load Cisco IOS Software to a router in ROMMON mode; this is typically done using TFTP or Xmodem.

* C: While a router can act as an FTP server, this is not a description of FTP itself.

* D: FTP uses TCP as its transport protocol, not UDP. FTP needs the reliability that TCP provides because it ensures the complete and accurate transfer of files1.

The configuration register on Cisco devices controls how the device boots up. By changing the configuration register to 0x2142, you instruct the router to bypass the startup configuration file stored in NVRAM. This is crucial in the password recovery process because the passwords are stored in this configuration file.

Procedure for Password Recovery:

1. Break the boot sequence: Power cycle the router (turn off/on). During the boot process, send a 'Break' signal to get into ROMmon mode.

2. Change the configuration register: In ROMmon mode, type confreg 0x2142 and reload the router.

3. Boot without startup-config: The router will boot up, ignoring the saved startup configuration, allowing you to enter privileged EXEC mode without a password.

4. Change the password: Access configuration mode (configure terminal), and change the passwords as needed (enable password, enable secret, etc.).

5. Reset the configuration register: Set the configuration register back to its original value (usually 0x2102).

6. Save changes: Save the new configuration with copy running-config startup-config.

* A. SSH...secure remote access: This is correct. SSH (Secure Shell) is designed specifically for secure remote access. It utilizes strong encryption to protect data transmissions, including login credentials and commands.

* B. Telnet...secure remote access: This is incorrect. Telnet is inherently insecure as it transmits all data, including sensitive passwords, in cleartext.

* C. SSH uses...TCP port 23: This is incorrect. SSH uses TCP port 22 by default, while Telnet uses TCP port 23.

* D. Telnet preferred...security reasons: This is incorrect. SSH is vastly preferred over Telnet due to its strong security features.

* E. Telnet connection...router reboots: This is correct. Telnet connections are not persistent, so a router reboot disrupts them. This re-enforces their lack of suitability for critical management tasks.

Key Points:

* Security: SSH is the recommended protocol for remote access to network devices due to its strong encryption and authentication mechanisms.

* Persistence: Telnet connections are temporary and get disrupted on events like router reboots.