100-490 Questions and Answers

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 ping command is specifically designed to test network connectivity and reachability. Here's how it works:

Echo Request: The ping command sends an ICMP (Internet Control Message Protocol) Echo Request packet to a specified destination IP address or hostname.

Echo Response: If the target host is reachable, it will respond with an ICMP Echo Reply packet.

Analysis: The ping command measures the round-trip time (RTT) between the source and destination. It also reports statistics like packet loss and response times.

Why other options are incorrect:

echo: In some command-line environments, the echo command is used to display text on the screen and does not relate to network testing.

access: This is a general term and does not refer to a specific command for sending echo requests.

connect: Some tools use the connect command to establish a TCP connection to a remote host, but it doesn't directly utilize ICMP echo packets like the ping command.

References:

ping (Wikipedia): https://en.wikipedia.org/wiki/Ping_(networking_utility)

The type of memory used to store Cisco IOS Software permanently is flash memory. Flash memory is non-volatile, meaning it retains its content even after the device is powered down or restarted. It is commonly used in Cisco devices to store one or more Cisco IOS software images, as well as other files such as backup configuration files. This allows the device to reload the operating system after a reboot without the need to retransfer the IOS image

When deploying Cisco Catalyst 3850 Series switches, there are two modes of operation to choose from: Install mode and Bundle mode. Install mode is the default mode for the switch and uses a package-provisioning file named packages.conf to boot the switch. It allows for a more complete set of features and requires fewer resources upon boot1. Bundle mode, on the other hand, is similar to using traditional monolithic Cisco IOS images to boot the switch. It consumes more memory than Install mode because the packages are extracted from the bundle and copied to the RAM2. Cisco recommends using Install mode for operation due to its efficiency and feature set2.

The address that facilitates the routing of packets over an IP network is the network address. In the context of IP networking, this refers to the IP address, which is used to identify each host on a network and to determine the best path for data packets to travel from their source to their destination. Routers use IP addresses to make decisions about where to forward packets so that they reach the correct destination. The network layer of the OSI model, where IP operates, is responsible for this routing process123.

The other options listed do not facilitate routing in the same way:

Physical (A) and MAC (D) addresses are used at the data link layer to deliver packets on the same local network.

Transport (B) refers to the transport layer, which is responsible for end-to-end communication and data flow control but does not route packets over an IP network.

The correct IPv6 address notation follows the format of eight groups of four hexadecimal digits, separated by colons. The address must have exactly eight groups unless it uses the double colon (::) to represent consecutive groups of zero value. The double colon can only appear once in an address to avoid ambiguity.

Option A is incorrect because it includes a subnet mask (/128) which is not part of the actual address notation. Option B is incomplete as it does not contain enough groups and ends with a single colon. Option C has too many groups (nine instead of eight) and is therefore not a valid IPv6 address. Option D is the correct notation with eight groups of four hexadecimal digits, where necessary leading zeros are included.

References :=

IPv6 Address Types, Notation, and Structure Explained1.

IPv6 address formats - IBM2. =========================

A. Correct. SSH, or Secure Shell, is indeed a protocol that provides a secure remote access connection to network devices. It encrypts the data to ensure secure transmission over insecure networks like the internet1.

C. Correct. Telnet connections are not secure and are terminated when a router reboots. This is because Telnet does not have any mechanism to maintain the connection in case of network interruptions or device reboots1.

B, D, and E are incorrect because: B. SSH uses TCP port 22 by default, not port 23, which is used by Telnet1. D. Telnet does not provide a secure connection; it transmits data in plain text, which can be intercepted easily1. E. SSH is preferred over Telnet for security reasons because it provides encrypted connections and authentication mechanisms, which Telnet does not1.

References :=1: GeeksforGeeks - Difference between SSH and Telnet 2: phoenixNAP - Telnet vs. SSH: How Is SSH Different From Telnet? 3: Guru99 - Telnet vs SSH – Difference Between Them 4: Difference Between - Difference Between Telnet and SSH

TFTP, or Trivial File Transfer Protocol, is a simple protocol used for transferring files. Unlike other file transfer protocols, TFTP operates on top of the User Datagram Protocol (UDP), which is a connectionless protocol. This means that TFTP does not establish a persistent connection between the client and server, and it does not guarantee reliable delivery of packets, error checking, or correction. TFTP is typically used in scenarios where simplicity and minimal memory footprint are more critical than the need for reliable delivery, such as when booting a device over a network123. References := Wikipedia, GeeksforGeeks, PyNet Labs

A DTE (Data Terminal Equipment) device is an end instrument that converts user information into signals or reconverts received signals. In the context of networking, a router can be considered a DTE device because it is typically at the user end of a user-network interface and serves as a data source or destination. It communicates with the data circuit-terminating equipment (DCE), such as a modem, to send and receive data across the network345.

References := Wikipedia, Techopedia, Network Encyclopedia

The data link layer of the OSI model, which is Layer 2, defines how data is formatted for transmission and controls access to the physical media. This layer is responsible for the node-to-node delivery of data and handles error detection and correction from the physical layer. It also manages the way data packets are sent over the network, including the framing, addressing, and flow control. The data link layer ensures that messages are delivered to the proper device on a LAN using hardware addresses (MAC addresses) and translates messages from the network layer into bits for the physical layer to transmit

For 40 Gigabit Ethernet connectivity, the type of transceiver module used is QSFP+ (Quad Small Form-Factor Pluggable Plus). QSFP+ modules are designed to carry 40-Gigabit Ethernet signals over fiber-optic or copper networking cables. They provide high-density and low-power 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider applications. QSFP+ modules are an evolution of the SFP+ (Small Form-Factor Pluggable Plus) modules, offering four times the bandwidth capacity1.

The Cisco Nexus 3432D-S and Cisco Nexus 3408-S are part of the Cisco Nexus 3400 Series switches that support 400-Gbps Ethernet ports. The Cisco Nexus 3432D-S is designed with 32 ports of 400G, providing high-density and high-throughput capabilities1. The Cisco Nexus 3408-S offers flexibility with 100G or 400G Line-Card Expansion Modules (LEMs), allowing for configurations with 32 ports of 400G2. These switches are engineered for data centers requiring high performance, low latency, and power efficiency, with the Cisco Nexus 3432D-S offering industry-leading performance-per-watt power efficiency at low latency1.

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)

Questions no: 12 Verified Answer: = B. switch-to-router, E. switch-to-server Comprehensive and Detailed Step by Step Explanation: = RJ-45 straight-through cables are used to connect different types of devices in a network. The standard practice is to use straight-through cables for connections that are unlike to each other, such as:

Switch-to-Router: A switch connects devices within a network by using MAC addresses to forward data to the correct destination. A router, on the other hand, connects multiple networks and uses IP addresses to determine the best path for the data packets. Connecting a switch to a router requires a straight-through cable because they are different types of devices12.

Switch-to-Server: Servers are the powerful computers that provide resources, data, services, or programs to the client machines in the network. When connecting a switch to a server, a straight-through cable is used because the switch and the server are different types of devices with different functions within the network12.

References := Guru99, TheTechMentor

The commands that can be used to identify the serial number of a Cisco router are show inventory and show version. The show inventory command provides detailed information about the hardware inventory, including the serial numbers of the device and its components1. The show version command displays the router’s configuration, including the version of the operating system, the last reboot reason, and the hardware serial number, which is listed as the “Processor board ID” in the command output2. These commands are essential for network administrators to document and manage network equipment.

The show environment command in Cisco devices is used to display the status of the system’s environment, including power supplies and sensor temperatures. This command provides a comprehensive overview of the environmental conditions affecting the device, such as temperature readings and power supply status.

Option A, show hardware, is not specific to power supplies and sensor temperatures. Option B, show module, displays information about the network modules installed in the device but not the environmental conditions. Option D, show diag, is used for diagnostic purposes and does not specifically provide the status of power supplies and sensor temperatures.

Therefore, the correct answer is C, show environment, which is the command that specifically shows the status of power supplies and sensor temperatures in Cisco devices12.

References :=

Cisco Community discussions on power supply details1.

Cisco documentation on Environmental Monitoring and Power Management2.