Networking today

Host roles
 All computers that are connected to a network and participate directly in network communication are
classified as hosts
 Hosts can be called end devices (some hosts are also called clients)
 The term hosts specifically refers to devices on the network that are assigned a number for communication
purposes. This number identifies the host within a particular network. This number is called the Internet
Protocol (IP) address.
 An IP address identifies the host and the network to which the host is attached.
 Servers are computers with software that allow them to provide information, like email or web pages, to
other end devices on the network
 Each service requires separate server software, for example, a server requires web server software in order
to provide web services to the network
 A computer with server software can provide services simultaneously to many different clients
 Clients are a type of host, clients have software for requesting and displaying the information obtained from
the server, as shown in the figure

 An example of client software is a web browser, like Chrome or FireFox. A single computer can also run
multiple types of client software. For example, a user can check email and view a web page shile instant
messaging and listening to an audio stream. The table lists three common types of server software
Type Description
Email The email server runs email server software. Clients use mail client software, such as Microsoft
Outlook, to access email on the server
Web The web server runs web server software. Clients use browser software such as Windows Internet
Explorer, to access web pages on the server
File The file server stores corporate and user files in a central location. The client devices access these
files with client software such as the Windows File Explorer

Peer-to-peer
 Clients and server software usually run on separate computers, but it is also possible for one computer, to be
used for both roles at the same time.
 In small businesses and homes, many computers function as the servers and clients on the network. This
type of network is called a peer-to-peer network

 The advantages of peer-to-peer networking:

o Easy to set up
o Less complex
o Lower cost because network devices and dedicated servers may not be required
o Can be used for simple tasks such as transferring files and sharing printers
 The disadvantages of peer-to-peer networking:
o No centralized administration
o Not as secure
o Not scalable
 o All devices may act as both clients and servers which can slow their performance

End devices
 To distinguish one end device from another, each end device on a network has an address
 When an end device initiates communication,
 it uses the address of the destination end device to specify where to deliver the message
 an end device is either the source or destination of a message transmitted over the network

Intermediary devices
 intermediary devices connect the individual end devices to the network. They can connect multiple
individual networks to form an internetwork. These intermediary devices provide connectivity and ensure
that data flows across the network
 intermediary devices use the destination end device address, in conjunction with information about the
network interconnections, to determine the path that messages should take through the network. Examples
of the more common intermediary devices and a list of functions:

o regenerate and retransmit communication signals

o maintain information about what pathways exist through the network and internetwork
o notify other devices of errors and communication failures
o direct data along alternate pathways when there is a link failure
o classify and direct messages according to priorities
o permit or deny the flow of data, based on security settings

Network media
 Communication transmits across a network on media. The media provides the channel over which the
message travels from source to destination
 Modern network primarily uses 3 types of media to interconnect devices:
o Metal wires within cables – data is encoded into electrical impulses
o glass or plastic Fibers within cables (fibber-optic cable) – data is encoded into pulses of light
o wireless transmission – data is encoded via modulation of specific frequencies of electromagnetic
waves
 The 4 main criteria for choosing network media are these:
o what is the maximum distance that the media can successfully carry a signal?
o whit is the environment in which the media will be installed?
o what is the amount of data and at what speed must it be transmitted?
o what is the cost of the media and installation?
Network representations and topologies
Network representations
 Diagrams of networks often use symbols, like those shown in the figure, to represent the different devices
and connections that make up a network

 A diagram provides an easy way to understand how devices connect in a large network. This type of
„picture“ of a network is known as a topology diagram. The ability to recognize the logical representations
of the physical networking components is critical to being able to visualize the organization and operation
of a network
 In addition to these representations, specialized terminology I sused to describe how each of these devices
and media connect to each other:
o network interface card (NIC) – a NIC physically connect the end device to the network
o physical port – a connector or outlet on a networking device where the media connects to an end
device or another networking device
o interface – specialized ports on a networking device that connect to individual networks. Because
routers connect networks, the ports on a router are referred to as network interfaces

Topology diagrams
 topology diagrams are mandatory documentation for anyone working with a network. They provide a visual
map of how the network is connected. There are 2 types of topology diagrams: physical and logical
Physical topology diagrams
 illustrate the physical location of intermediary devices and cable installation, as shown in the figure
 you can see that the rooms in which these devices are located are labered in this physical topology
Logical topology diagrams
 Illustrate devices, ports, and the addressing scheme of the network, as shown in the figure
 You can see which end devices are connected to which intermediary devices and what media is being used

Common types of networks

Networks of many sizes
 Networks come in all sizes. They range from simple networks consisting of 2 computers, to networks
connecting millions of devices
 simple home networks let you share resources, such as printers, documents, pictures and music, among
a few local end devices
 small office and home office (SOHO) networks allow people to work from home or a remote office. Meny
self-employed workers use these types of networks to advertise and sell products, order supplies and
communicate with customers
 businesses and large organizations use networks to provide consolidation, storage, and access to information
on network servers. Networks provide email, instant messaging and collaboration among employees. Many
organizations use their network´s connection to the internet to provide products and services to customers.
 The internet is the largest network in existence. In fact, the term internet means a „network of networks“ i
tis collection of interconnected private and public networks
 In small businesses and homes, many computers function as both the servers and clients on the network.
This type of network is called peer-to-peer network

1. Small home networks connect a few computers to each other and to the internet
2. Small office and home office networks (SOHO) allows computers in a home office or a remote office to
connect to a corporate network, or access centralized, shared resources

3. Medium to large networks, such as those used by corporations and schools, can have many locations with
hundreds of thousands of interconnected hosts

4. World wide networks – the internet is a network that connects hundreds of millions of computers world-
wide

LANs and WANs

 Network infrastructures vary greatly in terms of:
o size of the area covered
o number of users connceted
o numbers and types of services available
o area of responsibility
 The 2 most common types of network infrastructures are Local Area Networks (LANs), and Wide Area
Networks (WANs). A LAN is a network infrastructure that provides access to users and end devices in
a small geographical area. A LAN is typically used in a department within an enterprise, a home or a small
business network. A WAN is a network infrastucture that provides access to other networks over a wide
geographical area, which is typically owned and managed by a larger corporation or a telecommunications
service provider. The figure shows LANs connected to a WAN
LANs
- A LAN is a network infrastructure that spans a small geographicala area. LANs have specific
characteristics:
o LANs interconnect end devices in a limited area such as a home, shool, office building or campus
o A LAN is usually administered by a single organization or individual. Administrative control is
enforced at the network level and governs the security and access control policies.
o LANs provide high-speed bandwidth to internal end devices and intermediary devices, as shown in
the figure

WANs
- The figure show a WAN which interconnects 2 LANs. A WAN is a network infrastructure that spans a wide
geographical area. WANs are typically managed by service providers (SPs) or Internet Service Providers
(ISPs).
- WANs have specific characteristics:
o WANs interconnect LANs over wide geographical areas such as between cities, states, provinces,
countries or continents
o WANs are usually admnistered by multiple service providers
o WANs typically provide slower speed links between LANs
The Internet
 The internet is a worldwide collection of interconnected networks (internetworks or internet for short). The
figure shows one way to view the internet

 Some of the LAN examples are connected to each other through a WAN connection. WANs are then
connected to each other. The red WAN connection lines represent all the varieties of ways we connect
networks. WANs can connect through coppper wires, fiber-optic cables, and wireless transmissions (not
shown)
 The internet is not owned by any individual or group. Ensuring effective communication across this diverse
infrastructure requires the application of consistent and commonly recognized technologies and standards as
well as the cooperation of many network administration agencies. There are organizations that were
developed to help maintain the structure and standardization of internet protocols and processes. These
organizations include the Internet Engineering Task Force (IETF), Internet Corporation for Assigned Names
and Numbers (ICANN), and the Internet Architecture Board (IAB), plus many others.

Intranets and Extranets

 Intranet is a term often used to refer to a private connection of LANs and WANs that belongs to an
organization. An intranet is designed to be accessible only by the organization´s members, employees, or
others with authorization
 An organization may use an extranet to provide secure and safe access to individuals who work for
a different organization but require access to the organization´s data. Here are some examples of extranets:
o a company that is providing access to outside suppliers and contractors
o a hospital that is providing a booking system to doctors so they can make appointments for their
patients
o a local office of education that is providing budget and personnel information to the schools in it
district
Internet Connections
Internet Access Technologies
 Home users, remote workers, and small offices typically require a connection to an ISP to access the
internet. Connection options vary greatly between ISPs and geographical locations. However, popular
choices include broadband cable, broadband digital subscriber line (DSL), wireless WANs, and mobile
services.
 Organizations usually need access to other corporate sites as well as the internet. Fast connections are
required to support business services including IP phones, video conferencing, and data center storage. SPs
offer business-class interconnections. Popular business-class services include business DSL, leased lines,
and Metro Ethernet.

Home and Small Office Internet Connections

a) Cable – typically offered by cable television service providers, the internet data signal transmit on the same
cable that delivers cable television. It provides a high bandwidth, high availability and an always-on
connection to the internet.
b) DSL – Digital Subscriber Lines also provide high bandwidth, high availability and an always-on connection
to the internet. DSL runs over a telephone line. In general, small office and home office users connect using
Asymmetrical DSL (ADSL), which means that the download speed is faster that the upload speed.
c) Cellular – Cellular internet access uses a cell phone network to connect. Wherever you can get a cellular
signal, you can get cellular internet access. Performance is limited by the capabilities of the phone and the
cell tower to which i tis connected.
d) Satellite – the availability of satellite internet access is a benefit in those areas that would otherwise have no
internet connectivity at all. Satellite dishes require a clear line of sight to the satellite.
e) Dial-up telephone – an inexpensive option that uses any phone line and a modem. The low bandwidth
provided by a dial-up modem connection is not sufficient for large data transfer although it is useful for
mobile access while traveling
 The choice of connection varies depending on geographical location and service provider availability.

Businesses Internet Connections

 Corporate connection options differ from home user options. Businesses may require higher bandwidth,
dedicated bandwidth, and managed services. Connection options that are available differ depending on the
type of service providers located nearby.
a) Dedicated leased line – leased lines are reserved circuits within the service provider´s network that connect
geographically separated offices for private voice and/or data networking. The circuits are rented at
a monthly or yearly rate.
b) Metro Ethernet – this is sometimes known as Ethernet WAN. Metre ethernets extend LAN access
technology into the WAN.
c) Business DSL – is available in various formats. A popular chois is Symmetric Digital Subscriber Line
(SDSL) which is similar to the consumer version of DSL but provides uploads and downloads at the same
high speeds.
d) Satellite – satellite service can provide a connection when a wired solution is not available.
 The choice of connection varies depending on geographical location and provider availability

The Converging Network

Traditional Separate Networks
 Consider a school built thirty years ago. Back then, some classrooms were cabled for the data network,
telephone network, and video network for televisions. These separate networks could not communicate with
each other. Each network used different technologies to carry the communication signal. Each network had
its own set of rules and standards to ensure successful communication. Multiple services ran on multiple
networks.

Converged Networks
 Today, the separate data, telephone, and video networks converge. Unlike dedicated networks, converged
networks are capable of delivering data, voice, and video between many different types of devices over the
same network infrastructure. This network infrastructure uses the same set of rules, agreements, and
implementation standards. Converged data networks carry multiple services on one network.
Reliable networks

IOS Navigation
Primary Command Modes
- As a security feature, the Cisco IOS software separates management access into the following 2 command
modes:
o User EXEC mode
o Privileged EXEC mode

Command mode description Default Device

prompt
User Exec mode mode allows access to only a limited number of basic monitoring Switch>
commands Router>
it is often referred to as “view-only” mode
Privileged Exec Mode allows access to all commands and features Switch
mode The user can use any monitoring commands and execute Router
configuration and management commands

Configuration Mode and Subconfiguration Modes

- To configure the device, the user must enter global configuration mode, which is commonly called 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
Swithc(config)

year