Cisco IOS Modes of Operation EXEC | Privileged | Global configuration mode

Cisco IOS Modes of Operation EXEC | Privileged | Global configuration mode

This article is about the Cisco IOS Modes of Operation that are EXEC mode, Privileged mode and Global configuration mode. You will learn a brief introduction of all these Cisco IOS configuration modes & Cisco IOS bakup restore. Following are the main command modes are:

1. User EXEC Mode (>) 
2. EXEC Mode with privileges (#) 
3. Global configuration mode (config#)

The User Execution Mode  is useful in case of some basic operations that have to do with monitoring or consultation, but does not allow the execution of any command that can change the configuration of the device. For its part, the  privileged Execution Mode allows you to enter the global configuration mode and the highest configuration modes.

NAVIGATION BETWEEN IOS MODES

Once you understand the execution modes (which are only two), the navigation between the modes is also done through commands and these are the first commands you should learn:

With the enable command, you can  enter EXEC mode with privileges.
With the exit command, you can exit the previous command mode in the hierarchy.

You can review the above figure for clear understanding of switching different Cisco IOS Modes of Operation.

COMMAND MODE SETTINGS

The image above shows new ways that you should know and are very simple:

• To configure the device, the user must enter the global configuration mode, using the configure terminal command
• The global configuration mode is identified by an input request that ends with (config) # after the device name, such as Switch (config) #
• Subconfiguration modes can be accessed from the EXEC mode with privileges.
• Some examples: switch (config-line) # and switch (config-if) #

THE IOS COMMAND STRUCTURE
Let's see the basic structure of IOS commands:

• The general syntax for a command is the command followed by the corresponding keywords and arguments.
• Keyword : a specific parameter defined in the operating system
• Argument : not predefined; is a user-defined value or variable

Cisco IOS SUPPORT FEATURE

The IOS has two forms of help available if you do not remember any command: contextual help and the command syntax checker. Let's look at practical examples to use when we forget the commands.

CONTEXTUAL HELP

• Command options ( "characters" + "?" ): A list of commands or keywords that begin with those "characters" is displayed.

Switch # cl?
clear clock

• Command explanation ( "keyword" + "?" ): It shows what arguments or variables of the command can be written and provides an explanation of each.

Switch # clock set?
 hh: mm: ss Current Time

Switch # clock set 14:09:00?
 <1-31> Day of the month
 MONTH Month of the year

COMMAND SYNTAX VERSIFIER

• Incomplete command : It returns a help message indicating that the necessary keywords or arguments were omitted from the end of the command.

Switch # clock set
% Incomplete command

• Ambiguous Command : Returns a help message indicating that not enough characters were entered for the command interpreter to recognize.

Switch # d
% Ambiguous command: "d"

• Invalid argument : IOS returns a “^” to indicate which part of the command interpreter cannot be decrypted.

Switch # clock set 19:50:10 28 8
                             ^
% Invalid input detected at '^' marker.

SHORTCUT AND SHORTCUT KEYS

Commands and keywords can be shortened to the minimum number of characters that identifies a unique selection. For example, the configure command can be shortened to conf , since configure is the only command that starts with conf .

Cisco IOS Hotkeys  

Key	Description
Tabulation	Complete partial command name entry
Recoil	Delete the character to the left of the cursor
Ctrl + D	Delete the character after the cursor
Ctrl + K	Delete all characters from the cursor
Esc + D	Delete all characters from the cursor to the end of the word
Ctrl + U / X	Delete all characters
Ctrl + W	Delete the word to the left of the cursor
Ctrl + A	Move the cursor to the beginning of the line
Ctrl + E	Move the cursor to the end of the line / td>
Down arrow	It allows to move forward through the previous commands.
Up arrow	It allows you to scroll back through the previous commands.
Ctrl + Shift + 6	It allows the user to interrupt an IOS process, such as ping or traceroute.
Ctrl + Z	When in any configuration mode, finish the configuration mode and return to privileged EXEC mode

What is Cisco IOS ? Features how to Access a Cisco Router

What is Cisco IOS ? Features how to Access a Cisco Router?

This article is an introduction to the operating system of Cisco devices. What is Cisco IOS ? Features & how to download? All network devices and terminal require an operating system (OS). Cisco OS has three parts:

1. Shell , which is the part that interacts with the applications and the user.
2. Kernel, which is part of the OS that communicates with the PC hardware.
3. Hardware , which is the physical part of the computer.

WHAT IS CISCO IOS?

Cisco IOS is a set of network operating systems used in Cisco devices, which allows users to interact with those devices. All Cisco network devices come with a default IOS and it is possible to change the version or feature set of the IOS. We as users can interact with the shell through the command line interface (CLI) or the graphical user interface (GUI). While the CLI is a text-based environment, a GUI, such as Windows, SO X, Apple IOS or Android, allows the user to interact with the system in an environment that uses graphic icons, menus and windows.

Cisco IOS allows a network engineer to run CLI-based network programs and to enter text-based commands to configure these Cisco IOS.

The switch or router IOS provides options for the following:

• Configure interfaces on devices
• Enable routing and switching functions
• Configuration of different protocol on Cisco devices

The Cisco IOS is stored in flash memory, this means the following:

• It is a non-volatile storage: the information is not lost when the power is cut.
• It can be modified or overwritten as necessary.
• It can be used to store several versions of IOS.
• The IOS is copied from flash memory to volatile RAM.
• The amount of flash memory and RAM determines which IOS can be used.

What are Cisco IOS FUNCTIONS?

The main functions that Cisco routers and switches perform or enable include the following: 

1. Security
2. Routing
3. QoS
4. Addressing
5. Resource Management and Interface

How to Access a Cisco Router?

As I mentioned above you can interact with the OS shell. There are several ways to access the CLI environment and configure the device. The most common methods are as follows:

• Console
• Assistant
• Virtual terminal (Telnet / SSH)

Access Cisco Router through CONSOLE PORT

• The device can be accessed even if there are no network services configured (out of band).
• Form used for initial device configuration .
• You need a special console cable .
• Allows configuration commands to be entered.
• It must be configured with passwords to prevent unauthorized access.
• The device must be located in a secure room so that the console port cannot be easily accessed.

How to Access Cisco Router through AUXILIARY PORT

• Out of band connection.
• Use the telephone line .
• It can be used as a console port.
• Cisco catalytic switch does not have an auxiliary port .

VIRTUAL TERMINAL

There are two ways, through Telnet or by Secure Shell (SSH)

• Telnet
• Method to access the CLI remotely through a network.
• Requires active network services and that there is an active interface configured.

• Secure Shell (SSH)
• Remote login similar to Telnet, but uses more security .
• It has more secure password authentication.
• Use encryption when transporting data.

TERMINAL EMULATION PROGRAMS

To connect to a network device using the aforementioned access methods, there are a variety of programs such as:

• PuTTY
• SecureCRT
• HyperTerminal 
• Tera Term 
• OS X Terminal

Cisco Routet IOS image Backup & restore

Types of Computer Networks LAN WAN MAN

Types of Computer Networks LAN WAN MAN

This article is about the Types of Computer Networks. There are two most common types of network infrastructure of computer are Local Area Network (LAN) and Wide Area Network (WAN), but there are more.
It is important to keep in mind that network infrastructures can vary greatly in terms of:

• The size of the area they cover.
• The number of connected users.
• The quantity and types of services available.
• The area of ​​responsibility.

TYPES OF NETWORKS

The most common types of computer networks are the following:

1. Local Area Network (LAN)
2. Wide area network (WAN)
3. Metropolitan Area Network (MAN)
4. Wireless LAN (WLAN)
5. Networks Storage Area (SAN)

LOCAL AREA NETWORKS (LAN)

It is that Network that provides connectivity in a home, building or campus and we can highlight the following:

• They cover a small geographical area
• They interconnect terminals in limited areas. (For example: House, Buildings, campus)
• They are managed by a single organization
• Provide high speed bandwidth to internal devices

Following is the simple network topology diagram.

WIDE AREA NETWORKS (WAN)

They are those network infrastructures that cover a large geographical area. It has the following characteristics:

• They interconnect LAN networks across large geographic areas.
• They are managed by several service providers
• Provide slower speed links between LAN networks
• LANs that are geographically separated are connected by a WAN, operated by ISPs

MAN, WLAN AND SAN NETWORKS

Metropolitan Area Network (MAN)Metropolitan Area Network : Metropolitan Area Network - these are network infrastructures that cover a physical area larger than that of a LAN but less than that of a WAN (for example, a city). Typically, the MAN operation is run by a single entity, such as a large organization.

• Wireless LAN (WLAN) : Wireless Local Area Network - are similar to LANs, only that they wirelessly interconnect users and endpoints in a small geographic area.
• Storage Area Network (SAN) : Storage Area Network - are network infrastructures designed to support file servers and provide data storage, recovery and replication.
• Personal Area Network (PAN) : PAN - Personal Area Network - is definitely the smallest type of network you can use today and the name comes from the personal area network. You've probably used this in the last week without even knowing it. It is the interconnected network of technological devices available to an individual, but generally limited to a maximum of 10 meters.

INTRANET NETWORKS AND EXTRANET NETWORKS

The Internet is called “network of networks”, it is the global set of interconnected networks and is not owned by any person or group.

• Intranet : Used to refer to a private LAN and WAN connection that belongs to an organization and is designed to be accessed only by members and employees of the organization or other authorized persons.
• Extranet : Used to provide secure access to people who work for another organization, but require company data. Eg a company that provides access to external suppliers and contractors.

INTERNET ACCESS TECHNOLOGIES

There are several different ways to connect users and organizations to the Internet. Let's see how we classify these technologies:

• Domestic Internet or Small offices : Require an Internet Service Provider (ISP)

1. Broadband cable: Generally a service offered by cable television service providers.
2. Broadband per digital subscriber line (DSL): The digital subscriber line provides an always active and high-bandwidth Internet connection.
3. Wireless WAN and Mobile Services: Internet access by mobile data.

• Service providers (SP)  or Business : Service providers (SP) are those who provide business-level interconnections. To support business services, such as IP telephony, video conferencing and data center storage, fast connections are required.

1. Business DSL: It is available in various formats. A widely used option is the symmetric digital subscriber line (SDSL), which is similar to the consumer DSL version, but provides the same upload and download speeds.
2. Leased lines: Actual reserved circuits within the service provider's network.
3. Ethernet meter

Network Diagram or Network Representations | Topology Diagram

Network Diagram or Network Representations | Topology Diagram

To representing a network we use different symbol and topology icon, and this Topology Diagram known as Network Diagrams. In this section we will see the Logical Topology Diagrams and the Physical Topology Diagrams. The topology diagrams are mandatory for everyone working with networks. This is how a network is represented.

Network Symbols

Network diagrams use symbols / images to represent the different devices and connections that make up a network. A diagram allows you to easily understand the way in which devices are connected in a large network. This type of representation of a network is called a topology diagram . The ability to recognize the logical representations of physical network components is essential to visualize the organization and operation of a network.

In addition to these representations, specialized terminology is used when talking about how these devices and the media connect to each other. Some important terms to remember are:

• Network interface card: A NIC, or LAN adapter, provides the physical connection to the network on the PC or other terminal. The means that connect the PC to the network device are connected directly to the NIC.
• Physical port: a connector or connection on a network device where the media is connected to a terminal or other network device.
• Interface: specialized ports on a network device that connects to individual networks. Since routers are used to interconnect networks, the ports of a router are known as network interfaces.

TYPES OF NETWORK DIAGRAMS

Topology diagrams are mandatory for everyone who works with networks. These diagrams provide a visual map that shows how the network is connected.

There are two types of topology diagrams:

PHYSICAL TOPOLOGY DIAGRAM

Identify the physical location of the intermediary devices and the installation of the cables.

LOGIC TOPOLOGY DIAGRAM

Identify devices, ports and addressing scheme.

In summary, the topologies shown in the physical and logical diagrams are appropriate for your level of understanding at this point in the course. 

Computer Network Infrastructure and Component

Computer Network Infrastructure and Component

In this article we describe Computer Network Infrastructure and Component that is Devices, Media and Services with some common examples.

The route that takes a message from the origin to its destination can be as simple as a single cable that connects one PC to another or, as complex as a network that literally covers the world. This network infrastructure provides the stable and reliable channel through which communications occur.

The network infrastructure contains three categories of network components:

1. Network Devices
2. Network Media
3. Services

The devices and the media are the physical or hardware elements of the network. Typically, the hardware is composed of visible components of the network platform, such as a laptop, a PC, a switch, a router, a wireless access point (Access Point) or the wiring used to connect those devices .

Network Devices

The network devices that people are most familiar with are called terminals . Some examples of network terminals are shown in the following figure:

A network device is the origin or destination of a message transmitted through the network. To distinguish one terminal from another, each terminal in the network is identified by an address . When a terminal initiates a communication, it uses the address of the destination terminal to specify where the message should be sent.

Some examples of terminals:

• Computers (workstations, laptops, file servers, web servers)
• Network printers
• VoIP phones.
• TelePresence Devices.
• Security cameras.
• Mobile portable devices (such as smartphones, tablet PCs, PDA and wireless debit and credit card readers, and barcode scanners)

INTERMEDIARY NETWORK DEVICES

These devices connect the individual terminals to the network and can connect several individual networks to form an internetwork . They provide connectivity and guarantee data flow throughout the network.

These devices use the address of the destination terminal, together with information on the network interconnections , to determine the route that messages must take through the network. In the figure, some examples of the most common intermediary devices are shown:

Functions of intermediary network devices:

• Regenerate and transmit the data signals.
• Keep information about the routes that exist through the network and 
• networking. (Routers)
• Direct the data in alternative paths when there is a link failure. (Routers)
• Report errors and communication failures.
• Sort and direct messages according to QoS priorities
• Allow or deny data flow according to security parameters. (Firewall)

NETWORK MEDIA

Communication through a network is transported by means. The medium provides the channel through which the message travels from the origin to the destination.


Modern networks mainly use three types of means to interconnect devices and provide the route by which data can be transmitted. As shown in the following figure, these means are as follows:

TYPES OF NETWORK MEDIA

• Metal wires inside cables : the data is encoded in electrical impulses.
• Glass or plastic fibers (fiber optic cable): the data is encoded as light pulses.
• Wireless transmission : data is encoded with wavelengths of the electromagnetic spectrum.

To know what network medium we should use, let's take into account the following criteria.

CRITERIA FOR CHOOSING A NETWORK MEDIUM

• The distance by which the media can carry a signal correctly
• The environment in which the media will be installed
• The amount of data and the speed at which it should be transmitted
• The cost of the medium and the installation

NETWORK SERVICES

Finally, the services include a large number of common network applications that people use daily, such as email hosting services and web hosting services. The processes provide the functionality that directs and moves messages across the network. The processes are less obvious to us, but they are critical to the operation of the networks.

THE NETWORK AS A PLATFORM

If we look at separate traditional networks, we could realize that each network has its own rules and standards. These separate networks could not communicate with each other and each network would use different technologies to transport the communication signal.

Advances in technology allow us to consolidate these different types of networks on a platform known as "convergent network", which is the ability to transmit data, voice and video over the same
network infrastructure . A single network channel capable of sending these forms of communication.

THE NETWORK ARCHITECTURE

Networks must support a wide variety of applications and services, as well as operate through the different types of cables and devices that make up the physical infrastructure. The architecture of the network refers to the technologies that support the infrastructure and the services and the rules, or protocols, programmed that transfer the data through the network.

As networks evolve, we discover that there are four basic features that the underlying architectures need to meet user expectations:

• Fault tolerance : These networks depend on several routes between the origin and destination of the message. If a route fails, messages can be sent immediately by another link. The fact that there are several routes that lead to a destination is called "redundancy."
• Quality of service (QoS) : QoS becomes a primary mechanism to manage congestion and ensure reliable content delivery to all users. Congestion occurs when the demand for bandwidth exceeds the amount available. The bandwidth of the network is the measure of the amount of bits that can be transmitted in one second (bps).
• Security : The security of the infrastructure of a network includes the physical assurance of the devices that provide connectivity and prevent unauthorized access to the administrative software that resides in them.

Introduction to Computer Networks | What is LAN?

Introduction to Computer Networks | What is LAN?

As a first step on our path to CCNA certification we will touch on the topic of CCNA 1, Introduction to Computer Networks or what is LAN?
n this section we will be dealing with one of the first issues for CCNA certification called Network Fundamentals or Network Fundamentals. In today's world, we are connected as never before thanks to the use of networks, and that is how we perceive it in the news and discoveries that are known throughout the world in a matter of seconds, or, people who play with friends who are on the other side of the ocean and on other continents.

1. NETWORKS AND NEW FORMS OF COMMUNICATION

Internet globalization leads to new forms of communication that provide the ability to create information that can be accessed by a worldwide audience.

Some forms of communication you already know include the following:

• Text : allows two or more people to communicate instantly and in real time.
• Social media : they consist of interactive websites in which people and communities create and share user-generated content with friends, family, and the rest of the world.
• Collaboration tools : they allow people to communicate with each other, usually through real-time interactive video, without location or time zone limitations.
• Blogs : it is an abbreviation of the word weblogs and they are easy to update and edit web pages (such as  GNS3 Blog ).
• Wikis : these are web pages that user groups can edit and view together. While a blog is more like an individual and personal diary, a wiki is a group creation. As such, it may be subject to more extensive review and editing. (Example, Wikipedia)
• Podcasting : allows people to spread their audio recordings to a vast audience. The audio file is placed on a website (or blog or wiki) where others can download and play it on their PCs or other mobile devices.
• Peer-to-peer file sharing application (P2P): allows people to share files with each other without having to store them on a central server or download them from such a server. To join the P2P network, the user must simply install a P2P software.

What other sites or tools do you use to share what you think?

2. TYPES OF NETWORKS ACCORDING TO THEIR SIZE

There are networks of all sizes. They can range from simple networks, consisting of two PCs, to networks that connect millions of devices. Let's see some images to know more about the different sizes of networks.

• Small Networks : Small domestic networks connect some computers to each other and to the Internet. They are simple networks that are installed in homes allow you to share resources, such as printers, documents, images and music, between some local PCs.
• Office Networks (Home Offices) : Considered as medium sized networks, they allow computers in a home office or a remote office to connect to a corporate network and have access to centralized shared resources.
• Medium to Large Networks: Medium to large networks, such as those used in corporations and schools, can have many locations with hundreds or thousands of interconnected computers.
• World Networks : The Internet is a network of networks that connects hundreds of millions of computers worldwide. Internet is the most extensive network that exists. In fact, the term Internet means "network of networks." The Internet is literally a collection of interconnected private and public networks.

3. Clients & Servers in Computer network

In every computer network there are clients and servers. What does each of them mean and why is it important in computer networks? Let's also see what types of clients and servers exist.

All PCs connected to a network that participate directly in network communications are classified as hosts. The hosts are also called terminals.

WHAT IS A SERVER

The servers are PCs with software that allows them to provide information, for example email or web pages, to other terminals in the network. Each service requires a separate server software. For example, to provide web services to the network, a server needs a web server software. A PC with server software can provide services to one or more clients simultaneously. In addition, a single PC can run several types of server software.

TYPES OF SERVERS

1. File Server : The file server stores user and / or business files in a central location.
2. Web Server : The web server runs web server software and contains web pages.
3. Email Server : The email server runs email server software

WHAT IS A Clients?

Clients are PCs that have software installed that allows them to request information from the server and display the information obtained. A web browser, such as Chrome or Firefox, is an example of client software. A single PC can also run several types of client software. For example, a user can check their email and view a web page while using the instant messaging service and listen to the radio over the Internet.

TYPES OF CLIENT

• File Client : Client devices have access to these files through client software, such as Windows Explorer.
• Web Client : Customers use their browser software, such as Chrome, Opera or Firefox, to access the web pages found on the server.
• Email Client : Customers use their email client software, such as Microsoft Outlook, to access email messages found on the server.

4. PEER NETWORK (P2P)

Server and client software usually run on different computers, but it is also possible for the same computer to perform both functions at the same time. In small businesses and homes, many PCs function as servers and clients on the network. This type of network is called a peer network .

WHAT ARE P2P NETWORKS

P2P (Peer to Peer) or Peer-to-Peer networks are PCs that function as servers and clients on the network. A P2P network is made up of personal computers, each of which acts as a client and server, so that each one can exchange files directly with any other computer on the network. Each computer can access any of the others, although access can be restricted to those files that the user of a computer decides to make available. A Peer to Peer network is less expensive than client / server networks but less efficient when large amounts of data must be exchanged.

CHARACTERISTICS OF PEER NETWORKS

To determine what type, P2P or client / server, the network architecture to configure and use, you must consider:

• The type of user and the size of the organization.
• The peer-to-peer network is used in homes and small businesses because its implementation is economical and the user is the administrator.
• The client / server network is ideal for large corporations, schools and hospitals due to the large number of users and workstations it can accommodate, but it is more expensive than the point-to-point network.

THE ADVANTAGES OF PEER NETWORKS

The advantages of peer networks are presented below:

• Simple setup
• Less complexity
• Lower cost, since network devices or dedicated servers may not be required
• They can be used for simple tasks such as transferring files and sharing printers

THE DISADVANTAGES OF PEER NETWORKS

The disadvantages of peer networks are presented below:

1. Decentralized administration
2. They are not so safe
3. They are not scalable
4. All devices can function as clients and servers, which can slow performance

See you in a next post!