Notes for CCNA 200–125 -1
Hello everyone after a long time!
I will take the CCNA 200–125 exam next year. I have already started preparations for this.
I am planning to share a summary of my notes for the CCNA 200–125 exam on my blog. By doing so, I aim to create a resource for individuals who are interested in studying networking or preparing for various network certification exams.
In this article, we will introduce Networking, then we will look at topology types and finally we will touch on the OSI model. Happy reading.
What is Network?
A network is a structure where two or more devices (such as computers, printers, servers, etc.) are interconnected and share resources. There are certain devices that establish the connections between them, such as switches, routers, and similar devices.
The Characteristics of a Network:
- Topology
- Speed
- Cost
- Security
- Accessibility
- Scalability
- Stability
Types of Physical Topology
Bus Topology:
Bus topology, also called linear topology, is a network configuration in which all devices within the network are connected via a single central cable, such as an RJ-45 network cable or coaxial cable. It must be terminated at both ends with terminating resistors. Known as a bus, backbone, or trunk, this central cable facilitates data transmission between connected devices. Any disconnection will cause problems on the entire network. Not used today.
Ring Topology:
End devices are connected to their neighbors in a ring. It does not need to be terminated. A break in the ring affects all network devices. It is not used today.
Star Topology:
End devices are interconnected with an intermediate device such as a siwtch. A fault in this topology only affects that device. It is easy to install and has high scalability. It is the most commonly used topology type.
Mesh Topology:
Network devices are connected to each other via multiple media. The reason for this is that when there is a problem on any cable, the communication continues over the other cables connected.
OSI MODEL
The Open Systems Interconnection (OSI) model was developed as a standard model for network communications in the early 1980s. It consists of seven layers that define how computer systems communicate over a network. While the modern Internet is based on the simpler TCP/IP model, the OSI model is still widely used to understand and troubleshoot networks.
Introduced in 1983 by representatives from leading computer and telecommunication companies, the OSI model gained international recognition when it was adopted as a standard by the International Organization for Standardization (ISO) in 1984. Despite not being the primary model used in today’s Internet, the OSI model remains valuable for visualizing network operations and identifying and resolving networking issues.
7-) Application:
This layer allows users to access the network and enables communication between different application programs. Protocols like HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), and SMTP (Simple Mail Transfer Protocol) operate at this layer.
6-) Presentation:
This layer deals with the representation and conversion of data between different systems. It handles tasks such as data compression, encryption, and data format conversion.
5-) Session:
This layer establishes, manages, and terminates sessions between devices.
4-) Transport:
This layer ensures the secure and reliable delivery of data to the destination device. It performs functions like data segmentation, packet numbering, flow control, and error checking. Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) operate at this layer.
3-) Network:
This layer is responsible for routing data packets from the source to the destination. It performs functions like path selection, packet forwarding, and traffic control. The Internet Protocol (IP) operates at this layer.
2-)Data Link:
This layer provides a reliable point-to-point or point-to-multipoint connection and handles error detection and correction. It controls the transmission of data frames and recognizes devices’ physical addresses on the network.
1-) Physical:
This layer is responsible for the physical transmission of data over the network. It deals with converting data into physical signals such as electrical, optical, or radio waves.
That’s it for this week.
Next week, we will cover TCP/IP, data encapsulation, LAN, switches, and we will introduce Cisco IOS.
See you later.
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Contact
E-mail: mehmetdenizozkahraman@outlook.com
Linkedin: https://www.linkedin.com/in/mdenizozkahraman/
Twitter: @mdenizsec
