The knowledge about a Network is essential for a person to pass CCNA 100-101 ICND1 Exam as it is one of the major sections in the course outline.

What is a network?

It can be defined as a group of devices interconnected such that they can communicate and all of those devices are under one administrative domain of controls.

The three basic forms of computer networks are:

  • Local Area Network – LAN
  • Wide Area Network – WAN
  • Metropolitan Area Network – MAN
  • LAN:
    The local area network is consist of computer networks located in a same building or small geographical area. This type of network is mostly used in offices because it is the best way to share resources like printer, scanner or data storage etc. The advantage of this type of network is that it can be built at very low cost using hubs, Ethernet cables and network adapters.
  • WAN:
    The wide area network geographically covers a large area or he entire world. The best example for WAN is internet which connects the whole world together. A WAN network can have a number of LANs and MANs connected to each other.
  • MAN:
    The metropolitan area network is consist of computer networks in a city, college or a large building. MAN is larger than LAN but smaller than WAN, geographically. MAN can connect a number of LANs with each other and when MAN is deployed in a college campus then it is termed as Campus Area Network or CAN.


Physical Components of a Network:


In the above figure, if we want to share information from Computer in Network A to the Laptop in Network B, the message will be sent from Computer to the Switch A and as there is no direct connection between Switch A and Switch B, the message will be sent to the Router. The Router will transfer that message to the Switch B in Network B and the switch will finally forward it to the Laptop (the receiver).  We can say that routers or any other device that is capable of routing is necessary to share information between multiple networks as it acts as a bridge and provide a path for the flow of information. The routers also help us to connect our networks to the Wide Area Network or internet.

Data Storage Replication:
The data storage can be replicated locally (within a network) or can be replicated between the sites. This is helpful in case if we lose one of the data storage devices we can get that data from any other device replicated locally or on the internet via router.

OSI Model:
OSI stands for Open Systems Interconnection.  It is a set of rules developed so that the network devices made by different manufacturers like Cisco, IBM or HP can interconnect with each other as they all follow the OSI Model standards.

Impact of User Application on the Network:
The three main categories of user interaction with the network are

  • Batch Applications
  • Interactive Applications
  • Real-time Applications
  • Batch Applications:
    The batch applications can be taken in a sense that one machine is talking to another machine via a network. It involves FTP, TFTP, inventory updates and storage synchronization.


These two machines have their own databases and these are connected to each other so that the information can be moved for the purpose of synchronization. In this process there is no direct human involvement. The factor of bandwidth is very important but not critical in this scenario as it is directly proportional to the data transfer speed and synchronization.

  • Interactive Applications:
    It is not pure as Batch application because it directly have human interaction with the machine. It involves processes like inventory query and database update and it is two way communication i.e human send query to the database and the database returns result according to that query to the human / user. As it is a human-to-machine interaction, the response time is very important in this because humans consider the time as a valuable thing and the factor of response time becomes critical when the wait becomes excessive. The specific term of Latency is used to measure how fast or slow the data is transferred.
  • Real-time Applications:
    It is the most complex scenario can we can face. In this scenario human-to-human interaction in real-time is involved. Real-time applications involved VoIP, video and telephony etc. In this case end-to-end latency is so much critical.

Characteristics of a Network:
A network can have the following characteristics

  • Topology
  • Speed
  • Cost
  • Security
  • Availability
  • Scalability
  • Reliability
  • Topology:
    It refers to the layout of a network i.e the way in which devices are connected in a network. Different types of topologies are bus topology, ring topology, star topology and mesh topology.
  • Speed:
    It is one of the most important feature of a network that is directly associated to the user. Speed measures the time in which a specific amount of data is transferred per unit of time across a network.
  • Cost:
    It is also very important factor from the financial point of view and the business managers are always worried about the cost. They demand a high quality network at a reasonable price.
  • Security:
    Security of a network can never be neglected. The network should be secure enough so that the unauthorized persons could not enter a network or the important information should not be revealed to the unconcerned persons.
  • Availability:
    It means that the network should be active almost every time. If the users face problem at any time of the day in transferring data, it’s due to the poor availability.
  • Scalability:
    The network should be enough scalable so that the users / company can expand in their network easily with the passage of time and expansion of business.
  • Reliability:
    Reliability means that the organization / user can trust the network with confidence while sharing important / secret information across a network.

Physical Topologies:

Here we’ll discuss three types of topologies commonly used:

  • Bus Topology
  • Start Topology
  • Mesh Topology

Bus Topology:
It is the simplest form of physical topology in which all the devices in a network such as computer, laptop, printer, scanner etc are connected to a single cable called a bus with the help of connectors as shown in the figure below. The central main cable can be considered as the back bone of a network.



  • A network can be established in the form of bus topology very easily and moreover it’s very easy to expand this network.
  • It is a cheapest network in the sense of cost, it can be developed with very low budget.
  • This type of network is very suitable for Local Area Networks


  • The number of devices connected depends upon the length of central cable.
  • Whole network depends upon the central cable, if the central cable stops working due to some error, the whole network break down.
  • Proper terminals are required at the both ends of central cable to dump the signals.
  • It is difficult to trace any fault in this type of network.
  • It is not suitable for large and heavy traffic networks.

Start Topology:
In this type of topology, all the devices in a network are connected to a single central hub. The hub can be a router or switch


All the data in start topology is transferred from one device to another via central hub which also acts as a signal booster. The central hub can also join its network with the other networks.


  • The new devices can be added easily in start topology network without disturbing other devices.
  • As this type of network is centralized, it’s easy to monitor the performance.
  • If one of the devices / nodes in a network fails, it doesn’t affect the working of other devices in a network.


  • As the network depends upon the central hub so if the hub stops working, whole network breaks down.
  • It is an expensive form of network due to the use of switch or router as a central hub.
  • The network cannot be expanded easily because it directly depends upon the power or capacity of central hub.

Mesh Topology:
It is the most advanced and complex form of topology because each device in a network is connected to every other device.  Each node / device do not only sends or receives its own data but also act a path way for the communication between other two devices.

The mesh topology is further divided into two sub categories:

  • Full Mesh Topology
  • Partial Mesh Topology

Logical Topologies:
The logical topology can be defined as the logical paths which the signals use to move from one device to another for the purpose of data transfer. The logical topology is just like a logical address and can be changed.

Transparent Bridging:
A transparent bridge is a common type of bridge that observes incoming network traffic to identify media access control (MAC) addresses. These bridges operate in a way that is transparent to all the network’s connected hosts. This whole scenario is termed as transparent bridging.

The above discussion explains the working and types of the networks in detail. It is the basic knowledge that you must gain to excel your career in networking technology.

Visit the link below to get benefit from our Lesson 3 which focuses on Host-to-Host Communication in a network

Passing Cisco 100-101 Exam:
After getting all the technical knowledge about 100-101 exam, the candidate have to practice for better preparation of the real exam. The practice tests are a best tool / way to prepare for the real exam as it is a simulator of a real exam.