100-490 Sample Questions Answers

This configuration describes a crossover cable. A crossover cable is used to connect two similar devices directly, such as two computers or two switches, without the need for an intermediate device like a router. The wires at one end of a crossover cable are in reverse sequence to the wires at the other end, which allows the transmit and receive signals to be properly aligned between the two devices. This is different from a straight-through cable, where the wire sequence is the same at both ends1.

Ethernet

The typical physical connector used for a Gigabit Ethernet port is an RJ-45. This connector is standard for network cabling and provides the necessary performance for Gigabit Ethernet, which is also known as 1000BASE-T. RJ-45 connectors are used because they can support higher data rates compared to other connectors like RJ-11 or RJ-9, which are commonly used for telephone connections, and DB-25, which is an older serial port connector not suitable for high-speed Ethernet connections1.

References :=2: Ethernet Alliance - The Physical Layer of Ethernet 3: Altium - Gigabit Ethernet 101: Basics to Implementation 1: Ascent Optics - All You Need to Know About RJ45 Cables: Connectors, Interfaces, and… 4: Hardware Secrets - Gigabit Ethernet and How it works (a 2022 Guide)

SmartJacks are specialized devices used in telecommunications, particularly for T1/E1 lines. Here's why the correct answers make sense:

Signal Conversion: SmartJacks can convert between different signaling types (e.g., AMI to B8ZS). This is necessary because different telecommunication lines may use varying signaling standards.exclamation

Signal Regeneration: As signals travel over long distances, they can weaken and degrade.expand_more SmartJacks help regenerate the signal, ensuring that it maintains its strength and integrity throughout the transmission.expand_more

Why other options are incorrect:

Concentration point: SmartJacks are not primarily used as concentration points for dial-in/out connections.exclamation This function is typically handled by modems or other specialized devices.exclamation

Layer 2 operation: SmartJacks primarily operate at Layer 1 (Physical Layer) of the OSI model, focusing on the physical transmission of signals.

Channel Testing: While some SmartJacks may offer some basic channel testing capabilities, their primary functions are signal conversion and regeneration.

References:

SmartJack (Wikipedia): https://en.wikipedia.org/wiki/Smartjack

Loopback plugs are used to test the physical connections and configurations of network equipment. In a 56K modem loopback plug, the following pins are looped to create a test signal:

Pins 1 and 7 (Transmit): Looping the transmit pins back to each other allows the device to test its own signal transmission.

Pins 2 and 8 (Receive): Looping the receive pins back to each other allows the device to test its ability to receive its own signal.

Understanding RJ-45 Wiring:

RJ-45 connectors are standardized and have a specific pinout for various applications like Ethernet networking and analog telephony connections. You can find resources online that show the standard RJ-45 color coding and pin assignments.

The features associated with single-mode fiber-optic cable include:

Consists of a single strand of glass fiber: Single-mode fiber uses a single core (strand) of glass fiber to transmit light signals. This core is thinner than that of multimode fiber, allowing for greater transmission distances.

Carries a higher bandwidth than multimode fiber: Single-mode fiber can carry higher data rates over longer distances compared to multimode fiber. It is commonly used in long-haul communication links and high-speed networks.

References:

Single-mode vs. Multimode Fiber

Fiber Optic Cable Types

A Wide Area Network (WAN) connection typically involves several components that work together to enable data communication over large distances. Two key components of a WAN connection are:

CSU/DSU (Channel Service Unit/Data Service Unit): This device acts as a gateway between the local area network (LAN) and the WAN. It converts the digital signals used in the LAN to the signals used in the WAN, which are often analog12.

Router: A router is used to connect multiple networks together and direct data traffic. In the context of a WAN, routers are responsible for determining the best path for data to travel across the network12.

References := Spiceworks, Cisco

The show version command on Cisco devices provides a variety of system information, including:

Cisco IOS version: The version of the Cisco IOS software running on the device.

Boot image: The location of the IOS image used during startup.

Hardware information: Model, processor type, memory details.

Interfaces: A list of the device's interfaces.

Configuration register: The current value of the configuration register, typically displayed near the end of the output.

Why other options are incorrect:

show flash: Displays the contents of flash memory, but not the configuration register.

show running-config: Displays the currently active configuration, but the configuration register setting is not directly part of the running configuration.

show config-register: This is not a standard Cisco IOS command.

Cisco NX-OS has added support for Python scripting to help manage user networks. Python is a powerful and versatile scripting language that is widely used for automation tasks, including network management. Cisco NX-OS leverages Python to enable network administrators to write custom scripts and programs that can interact with the network operating system, automate repetitive tasks, and integrate with other systems and APIs. This support for Python scripting is part of Cisco’s commitment to network programmability and automation, allowing for more efficient and flexible network operations12.

The show inventory command in Cisco IOS is designed specifically to display detailed hardware inventory information about a Cisco device. This includes:

Component Name: The name or type of each module or card installed.

PID (Product ID): The unique product identifier for the module.

VID (Version ID): The version identifier for the module.

Serial Number: The unique serial number assigned to the module.

Why other options are incorrect:

show chassis: Some Cisco devices support a show chassis command, but the information provided usually focuses on the physical chassis rather than detailed component inventory.

show items: This is not a standard Cisco IOS command.

show router: This command doesn't provide the level of granular hardware information that show inventory does.

When you initially log in to a Cisco router, the default operating mode is user EXEC mode. This mode provides a limited set of basic monitoring commands but does not allow for any configuration changes to the router’s settings. To make configuration changes, you must enter privileged EXEC mode (often accessed by the enable command), which offers a wider range of commands that allow for the viewing and modification of the configurationGlobal configuration mode is accessed from privileged EXEC mode to modify the router’s configuration, and ROM monitor mode is a low-level mode used mainly for recovery purposes1.

The show cellular unit network command in Cisco IOS is used to view detailed information about the cellular modem and the network it's connected to. Here's the type of information this command usually displays:

Network Status: Whether the device is registered on the cellular network.

Carrier Information: The name of the cellular network provider.

Technology: The cellular technology in use (e.g., 3G, 4G/LTE).

Signal Strength: Signal strength indicators like RSSI and RSCP.

Cell Site Information: Data about the cell tower or base station the device is connected to.

IP Address: The IP address assigned to the cellular interface.

Why other options are less likely:

show cellular unit radio: Provides information about the radio module itself, such as its state and power levels.

show cellular unit hardware: Focuses on hardware-level information of the cellular unit.

show cellular unit profile: Displays configuration details of the cellular profile used to connect to the network.

References:

Cisco command documentation for different show cellular options: https://www.cisco.com/c/en/us/td/docs/routers/wireless-wan/Cisco-Catalyst-Cellular-Gateways/cisco-cellular-gateways-command-reference-guide/m-show_commands.pdf

The show ip interface brief command provides a concise summary of the status and IP addressing configuration of interfaces on a Cisco router or switch. Here's what it displays:

Interface: The name of the interface (e.g., FastEthernet0/0, GigabitEthernet1/1).

IP Address: The Layer 3 IP address assigned to the interface (if any).

OK? Indicates the IP layer status of the interface (YES if operational, NO if not).

Method: How the IP address was configured (manual or DHCP).

Status: The Layer 1 status of the interface (up or down).

Protocol: The Layer 2 status of the interface (up or down).

Why other options are incorrect:

Layer 2 address: The show ip interface brief command does not directly display Layer 2 (MAC) addresses. You can use the show interface command for that.

Keepalive: Keepalives are used in some routing protocols but are not generally reflected in the output of the show ip interface brief command.

Encapsulation type: Encapsulation information is also not typically included in the show ip interface brief output.

References:

Cisco IOS show ip interface brief command: [invalid URL removed]

Example output of show ip interface brief: https://www.cisco.com/E-Learning/bulk/public/tac/cim/cib/using_cisco_ios_software/cmdrefs/show_ip_interface.

RJ-45 is the standard connector used for Ethernet networks. Here's why it's the correct answer:

Compatibility: Ethernet ports on both laptops and Cisco switches use RJ-45 connectors. This makes RJ-45 cables ideal for direct connections between these devices.

Appearance: RJ-45 ports are rectangular and slightly larger than typical phone jacks (RJ-11). They have eight metal pins inside.

Why other options are incorrect:

DVI: DVI ports are used for video connections between computers and displays.

RJ-11: RJ-11 ports are primarily associated with analog phone lines and are smaller than RJ-45.

DB-9: DB-9 connectors were traditionally used for serial connections on older computers and peripherals.

The copy tftp flash command is used to download a Cisco IOS image from a TFTP (Trivial File Transfer Protocol) server and store it in the Flash memory of the Cisco device. Here's the breakdown of the command:

copy: Indicates a file transfer operation.

tftp: Specifies the use of the TFTP protocol.

flash: Specifies the destination as the flash memory of the Cisco device.

Why other options are incorrect:

copy tftp nvram: This would attempt to copy a file from a TFTP server to the NVRAM of the device. NVRAM is typically not the desired location for storing IOS images.

copy flash tftp: This command would copy a file from the local flash memory to a TFTP server (uploading).

copy xmodem flash: This would use the XMODEM protocol for the transfer, which is slower and less reliable than TFTP for Cisco IOS images.

https://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol

The cmd program, also known as the Command Prompt, is the primary command-line interface in Windows. It allows you to execute various commands, including the ping command, to perform network testing and troubleshooting.

Here's how to use ping in the Command Prompt:

Open the Command Prompt: Search for 'cmd' in the Windows Start Menu or use the Run dialog (Windows key + R) and type 'cmd'.

Type the ping command: Enter ping followed by a space and then either the IP address or hostname you want to test. For instance: ping 8.8.8.8 or ping www.google.com .

Press Enter: The Command Prompt will send ping requests and display the results.

Why other options are incorrect:

Find: The Find utility in Windows is used to search for files and folders based on their content or attributes.

Start: The Start Menu in Windows provides access to programs, settings, and power options.

ipconfig: The ipconfig command is used to display network configuration information but doesn't directly execute the ping command.

References:

Windows Command Prompt (cmd): https://en.wikipedia.org/wiki/Cmd.exe

Ping command: https://en.wikipedia.org/wiki/Ping_(networking_utility)

DRAM, or Dynamic Random-Access Memory, is the type of memory that is erased when a Cisco device is rebooted. DRAM is used to store the running configuration and routing tables of the device. Since DRAM is volatile memory, its contents are lost when the device is powered down or restarted. This is in contrast to non-volatile memory types like flash and NVRAM, which retain their contents even after a reboot1. References := Types of memory on a Cisco device - Study-CCNA

While the initial answers focused on the most common causes, here's why the other options could also contribute to an interface being stuck in the "up/down" state:

A. Speed or Duplex Mismatch: Devices on either end of an Ethernet connection need to use compatible speed (e.g., 100 Mbps, 1 Gbps) and duplex (full-duplex or half-duplex) settings. Mismatches can prevent the line protocol from coming up even if the physical link is established.

B. Layer 2 Mismatch in Encapsulation Type: Some protocols used on Ethernet networks, like ISL and 802.1Q, have specific encapsulation requirements. If devices on each end aren't using the same encapsulation type, the line protocol will likely remain down.

C. The Ethernet Interface Has Been Manually Disabled: Correct! Administrators can put an interface in a shutdown state using commands like shutdown. This brings down the line protocol even if the physical connection is good.

D. Keepalives Are Not Being Received by the Local Device: While less likely to be the sole cause, issues with keepalive mechanisms used in some routing protocols could potentially lead to the line protocol going down. If the local device expects keepalives and doesn't receive them, it might assume a connectivity problem and affect the interface status.

E. The Ethernet Cable Might Not Be Attached Properly: While a disconnected or faulty cable would usually make the interface down/down, it's possible in some scenarios for a partially connected or damaged cable to result in a link being detected (Layer 1 up) but with errors preventing the line protocol (Layer 2) from initializing.

Troubleshooting network issues often involves considering multiple factors and testing different possibilities. The "up/down" status gives important clues but might have several potential root causes.

The copy startup-config running-config command is used during the password recovery process on a Cisco router to load the saved configuration into the device's active running configuration. Here's why this is the correct choice:

Password Recovery Context: Password recovery often involves booting into ROMmon mode and changing the configuration register to bypass the normal boot process. This leaves the device with a blank running configuration.

Restoring Configuration: The copy startup-config running-config command copies the stored configuration (startup-config) from NVRAM into the running-config, which is used by the router for its operations.

Why other options are incorrect:

load_helper: While the load_helper command sometimes appears in password recovery procedures, it's typically used for older models and may not be necessary for all Cisco routers.

configure terminal: This command simply enters global configuration mode. It doesn't directly load a configuration.

copy running-config startup-config: This command saves the active running configuration into NVRAM as the startup-config. It's the reverse of what you need for password recovery.