Cisco IOS Technologies




A network is devices connected to end systems and able to communicate with each other.

Use of the network:

Sending data between computers, sharing files. Network printers.

Network Storage

Network backup server for services Real time applications like VOIP


  • END Points: Like computers, for example, they are sending and receiving data.
  • Network devices: Like switches which provide a network connection for your end devices.
  • Interconnections: Makes sure that data can go from a device to another like connector, network cards…
  • Routers: Routers interconnect networks and we will see in this course how they choose the best path to each network destination.


There are two main types of topology. Network topologies may be physical

or logical. Physical topology means the physical design of a network including the devices, locations, and cables. Logical topology is about how data is actually moved around in a network, not its physical design.

Physical Topology(picture 1):

Ring topology:

set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

Mesh topology:

Fully connected mesh topology

The number of connections in a full mesh network of n nodes is = n(n – 1) / 2. The fully connected mesh topology is generally too costly and complex for practical networks. It has been used on networks with only a small number of nodes.

Partially connected mesh topology

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Star topology:

In local area networks with a star topology, each network host (for example a PC) is connected to a central hub with a point-to-point connection. All traffic on the network passes through the central hub. The hub acts as a signal booster or repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that it may need a lot more cables and if the hub breaks everything will stop working.

Bus topology:

In local area networks where bus topology is used, each machine is connected to a single cable. Each computer or server is connected to the single bus cable through some kind of connector. A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the MAC address or IP address on the

network that is the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data.

Picture 1

But before going deep there is a thing that you heard about it and maybe people don’t give it that important but we should know it which is THE OSI MODEL.

So what is OSI MODEL?

Its goal is the interoperability of diverse communication systems with standard will ask me what is this? Ok, I’ll be clear with you, before this model cames each vendor had his own solution so we couldn’t use different solutions of different vendors in the same network so this model came to make the interoperability exist thanks to International Organization for Standardization (ISO).