Explore The Network
1.2.1-1.2.3
The purpose of CISCO IOS
It is the embedded software architecture in all of the Cisco
routers and is also the operating system of the Catalyst switches
The Cisco IOS provides the following network services
Basic routing and switching functions
Reliable and secure access to networked resources
Network scalability
Operating System
◦ Windows, Mac, and Linux for PCs and laptops
◦ Apple iOS and Android for smart phones and tablets
◦ Cisco IOS for network devices (e.g., switches, routers, wireless AP, firewall, …)
Router user interface
The Cisco IOS software uses a command-line interface
(CLI) as the traditional console environment.
This environment is accessible through several methods
A console uses a low speed serial connection directly from a
computer or terminal to the console connection on the router.
A dialup connection using a modem or null modem connected
to the router AUX port.
Telnet to the router.
Purpose of OS
Using a GUI enables a user to:
Use a mouse to make selections and run programs
Enter text and text-based commands
Access Methods
The three most common ways to access the IOS are:
◦ Console port
◦ Secure Shell (SSH)
◦ Telnet
IOS Modes
User EXEC mode:The user EXEC mode allows only a limited number of basic
monitoring commands.
. Privileged EXEC mode: This mode can be configured to require a password from the
user before accessing it.
Global Configuration mode: This mode allows users to modify the running system
configuration.
Cisco CL
The Cisco IOS command-line interface (CLI) is the primary user interface used for configuring, monitoring, and maintaining Cisco devices.
This user interface allows you to directly and simply execute Cisco IOS commands, whether using a router console or terminal, or using remote access methods.
Navigate the IOS
Configuration Command Modes
The primary configuration mode is called global
configuration or simply, global config.
◦ Use the configure terminal command to access.
◦ Changes made affect the operation of the device.
Specific sub configuration modes can be accessed from global configuration mode. Each of these modes allows the configuration of a particular part or function of the IOS device.
◦ Interface mode - to configure one of the network interfaces.
◦ Line mode - to configure the console, AUX, Telnet, or SSH
access.
Various commands are used to move in and out of command
prompts:
◦ To move from user EXEC mode to privileged EXEC mode, use the
enable command.
◦ Use return to user EXEC mode, use the disable command.
Various methods can be used to exit / quit configuration
modes:
◦ exit - Used to move from a specific mode to the previous more
general mode, such as from interface mode to global config.
◦ end - Can be used to exit out of global configuration mode regardless
of which configuration mode you are in.
◦ ^z - Works the same as end.
The following provides an example of navigating between
IOS modes:
◦ Enter privileged EXEC mode using the enable command.
◦ Enter global config mode using the configure terminal command.
◦ Enter interface sub-config mode using the interface fa0/1
command.
◦ Exit out of each mode using the exit command
◦ The remainder of the configuration illustrates how you can exit a sub-config mode and return to privileged EXEC mode using either the end or ^Z key combination.
Basic IOS Command Structure
A Cisco IOS device supports many commands. Each IOS command has a specific format or syntax and can only be executed in the appropriate mode. The general syntax for a command is the command followed by any appropriate keywords and arguments.
•Keyword - a specific parameter defined in the operating system (in the figure, ip
protocols)
•Argument - not predefined; a value or variable defined by the user (in the figure, 192.168.10.5) After entering each complete command, including any keywords and arguments, press the Enter key to submit the command to the command interpreter.
IOS Command Syntax
To determine the keywords and arguments required for a command,
refer to the command syntax
◦ description string - The command is used to add a description to an interface. The string argument is text entered by the administrator such as description Connects to the main headquarter office switch.
◦ ping ip-address - The command is ping and the user-defined argument is the
ip-address of the destination device such as in ping 10.10.10.5
IOS Help Features
IOS Context-Sensitive Help:
◦ Context-sensitive help provides a list of commands and the
arguments associated with those commands
within the context of the current mode. ◦ To access context-sensitive help, enter a question mark ?, at any prompt.
IOS Command Syntax Check:
• The command line interpreter checks an entered command from left to right
to determine what action is being requested.
• If the interpreter understands the command, the requested action is
executed and the CLI returns to the appropriate prompt.
• If the interpreter discovers an error, the IOS generally provides feedback such as “Ambiguous command”, “Incomplete command”, or “Incorrect command”.
Hot Keys and Shortcuts
Commands and keywords can be shortened to the minimum number of
characters that identify a unique selection.
For example, the configure command can be shortened to conf because
configure is the only command that begins with conf.
◦ An even shorter version of con will not work because more than one
command begins with con.
◦ Keywords can also be shortened.
Hotkeys and Shortcuts
The IOS CLI support the following hotkeys:
Down Arrow – Allows the user to scroll through command history.
Up Arrow - Allows the user to scroll backward through commands.
Tab - Completes the remainder of a partially entered command.
Ctrl-A - Moves to the beginning of the line.
Ctrl-E – Moves to the end of the line.
Ctrl-R – Redisplays a line.
Ctrl-Z – Exits the configuration mode and returns to user EXEC.
Ctrl-C – Exits the configuration mode or aborts the current command
Ctrl-Shift-6 – Allows the user to interrupt an IOS process (e.g., ping).
Overview of Network Components
Computer networks components comprise both physical parts as well as the software required for installing computer networks, both at organizations and at home. The hardware components are the server, client, peer, transmission medium, and connecting devices. The software components are operating system and protocols.
End Device
The network devices that people are most familiar with are called end devices. These devices form the interface between the human network and the underlying communication network. Some examples of end devices are: Computers ,laptops, file servers, web servers.
Intermediary network device
Intermediary devices interconnect end devices.
These devices provide connectivity and work behind the scenes to ensure that data flows across the network.
switches and wireless access points (network access)
routers (internetworking)
firewalls (security).
Network Media
Network media refers to the communication channels used to interconnect nodes on a computer network.
Typical examples of network media include copper coaxial cable, copper twisted pair cables and optical fiber cables used in wired networks, and radio waves used in wireless data communications networks.
Network Representasation
The purpose of network representation is to learn a set of latent features by obtaining community information from network structures to provide knowledge for machine learning tasks.
Topology Diagram
The configuration, or topology, of a network is key to determining its performance. Network topology is the way a network is arranged, including the physical or logical description of how links and nodes are set up to relate to each other.