Chapter 2

Shell -

The user interface that allows users to request specific tasks from the computer. These requests can be made either through the CLI or GUI interfaces.

Hub -

Connects devices on a network-but sends traffic to everyone on the network

Switch -

Connects devices on a network-sends traffic only to the device it is intended for

Router -

Connects different networks together

Italic

italics text indicates arguments for which you supply values.[x]Square brackets indicate an optional element (keyword or argument).

Interface Configuration Mode -

Used to configure a switch port or router network interface. Switch(config-if)#

Console

A physical management port used to access a device in order to provide maintenance, such as performing the initial configurations. Out-of-band access refers to access via a dedicated management channel that is used for device maintenance purposes only. The advantage of using a console port is that the device is accessible even if no networking services are configured, such as performing the initial configuration. A computer running terminal emulation software and a special console cable to connect to the device are required for a console connection.

boldface

Boldface text indicates commands and keywords that you enter literally as shown

[x {y | z }]

Braces and vertical lines within square brackets indicate a required choice within an optional element. Spaces are used to clearly delineate parts of the command.

{x}

Braces indicate a required element (keyword or argument).

Backspace

Erases the character to the left of the cursor.

global config mode-

From global config mode, CLI configuration changes are made that affect the operation of the device as a whole. Global configuration mode is identified by a prompt that ends with (config)# after the device name, such as Switch(config)#. To return to privilege EXEC mode, use the exit command.

Left Arrow or Ctrl+B

Moves the cursor one character to the left.

Right Arrow or Ctrl+F

Moves the cursor one character to the right.

Up Arrow or Ctrl+P

Recalls the commands in the history buffer, beginning with the most recent commands.

Secure Shell (SSH)

SSH is an in-band and recommended method for remotely establishing a secure CLI connection, through a virtual interface, over a network. Unlike a console connection, SSH connections require active networking services on the device, including an active interface configured with an address. Most versions of Cisco IOS include an SSH server and an SSH client that can be used to establish SSH sessions with other devices.

AUX port

Similar to a console connection, this is a out-of-band and does not require networking services to be configured or available. This is also support is a legacy auxiliary port that was used to establish a CLI session remotely over a telephone connection using a modem.

the delimiting character

The "#" in the command syntax is called____________.

ping ip-address -

The command is ping and the user-defined argument is the ip-address of the destination device. For example, ping 10.10.10.5.

traceroute ip-address -

The command is traceroute and the user-defined argument is the ip-address of the destination device. For example, traceroute 192.168.254.254.

firmware

The operating system on home routers is usually called this_________. The most common method for configuring a home router is by using a web browser-based GUI.

Hardware -

The physical part of a computer including underlying electronics.

Dotted decimal

The structure of an IPv4 address is called______________ notation and is represented by four decimal numbers between 0 and 255.

running-config -

This is stored in Random Access Memory (RAM). It reflects the current configuration. Modifying a running configuration affects the operation of a Cisco device immediately. RAM is volatile memory. It loses all of its content when the device is powered off or restarted.

running-config-

This is stored in Random Access Memory (RAM). It reflects the current configuration. Modifying a running configuration affects the operation of a Cisco device immediately. RAM is volatile memory. It loses all of its content when the device is powered off or restarted.

Command syntax

check verifies that a valid command was entered by the user. If the interpreter cannot understand the command being entered, it will provide feedback describing what is wrong with the command.

Context-sensitive

help enables you to quickly find answers to these questions: Which commands are available in each command mode? Which commands start with specific characters or group of characters? Which arguments and keywords are available to particular commands?

DHCP

is a technology that is used in almost every network. The best way to understand why DHCP is so popular is by considering all the extra work that would have to take place without it

Telnet

is an insecure, in-band method of remotely establishing a CLI session, through a virtual interface, over a network. Unlike SSH, Telnet does not provide a secure, encrypted connection and should only be used in a lab environment. User authentication, passwords, and commands are sent over the network in plaintext. The best practice is to use SSH instead of Telnet. Cisco IOS includes both a Telnet server and Telnet client.

Tab

Completes a partial command name entry.

startup-config -

This is the saved configuration file that is stored in NVRAM. It contains all the commands that will be used by the device upon startup or reboot. Flash does not lose its contents when the device is powered off.

User EXEC Mode -

This mode has limited capabilities but is useful for basic operations. It allows only a limited number of basic monitoring commands but does not allow the execution of any commands that might change the configuration of the device. The user EXEC mode is identified by the CLI prompt that ends with the > symbol. Mode allows access to only a limited number of basic monitoring commands. It is often referred to as "view-only" mode.

Kernel

Communicates between the hardware and software of a computer and manages how hardware resources are used to meet software requirements.

dotted decimal notation

The structure of an IPv4 address is represented by four decimal numbers between 0 and 255.

Keyword -

This is a specific parameter defined in the operating system (in the figure, ip protocols).

Argument -

This is not predefined; it is a value or variable defined by the user (in the figure, 192.168.10.5).

Privileged EXEC Mode -

To execute configuration commands, a network administrator must access privileged EXEC mode. Higher configuration modes, like global configuration mode, can only be reached from privileged EXEC mode. The privileged EXEC mode can be identified by the prompt ending with the # symbol. To move from user EXEC mode to privilege EXEC mode, use the enable command. Mode allows access to all commands and features. The user can use any monitoring commands and execute configuration and management commands.

Line Configuration Mode -

To move in and out of line configuration mode, use the line command followed by the management line type. To return to global configuration mode, use the exit command. Used to configure console, SSH, Telnet, or AUX access. Switch(config-line)#

Subconfiguration Modes:

To move out of any subconfiguration mode to get back to global configuration mode, use the exit command. To return to privilege EXEC mode, use the end command or key combination Ctrl +Z. To move directly from one subconfiguration mode to another, type in the desired subconfiguration mode command. In the example, the command prompt changes from (config-line)# to (config-if)#.