Understanding Networking Essentials with Packet Tracer

As a software developer, we always wonder what’s the practical use of subjects like computer networks, so let's understand it's essential with packet tracer does clearing the concept in depth.

Quick revision on computer networks

A computer network is a group of computers and other devices that are connected together to communicate and share resources, such as data, printers, and internet connections. There are several types of networks, including local area networks (LANs), wide area networks (WANs), and home networks.

There are several devices that are used to build and maintain a computer network. Some common devices include:

• Routers: A device that connects multiple networks together and routes data between them.
• Switches: A device that connects devices within a network and forwards data between them.
• Hubs: A device that connects devices within a network and broadcasts data to all connected devices.
• Bridges: A device that connects two or more networks together and filters traffic between them based on the MAC addresses of the devices.
• Modems: A device that connects a computer to the internet and modulates and demodulates the data being transmitted.
• Access points: A device that allows wireless devices to connect to a network.
• Firewalls: A device or software that protects a network from unauthorized access and security threats.
• Network interface cards (NICs): A device that allows a computer to connect to a network using a wired connection.
• Wireless adapters: A device that allows a computer to connect to a network wirelessly.

An IP address (Internet Protocol address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. An IP address serves two main functions: host or network interface identification and location addressing.

A MAC address (Media Access Control address) is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used as network addresses for most IEEE 802 network technologies, including Ethernet.

Subnetting is the process of dividing a network into smaller subnetworks, or subnets. This is often done to improve network performance and security or to allow the network to be more easily managed.

In subnetting, the IP address of a device is divided into two parts: the network portion and the host portion. The network portion identifies the subnet, while the host portion identifies the specific device within the subnet. The subnet mask is used to determine which portion of the IP address belongs to the network and which portion belongs to the host.

For example, consider the IP address 192.168.1.100 with a subnet mask of 255.255.255.0. The first three octets (192.168.1) represent the network portion of the address, while the last octet (100) represents the host portion. This means that the device with this IP address is part of the 192.168.1 subnet and has the unique identifier 100 within that subnet.

There are two main types of IP addresses: public and private.

A public IP address is an IP address that is assigned to a device by an Internet service provider (ISP) and is used to communicate with devices on the internet. A public IP address is globally unique and can be accessed from anywhere on the internet.

A private IP address is an IP address that is assigned to a device within a private network, such as a home or office network. Private IP addresses are not unique globally and are used to communicate within the private network only. Private IP addresses are not accessible from the internet.

Private IP addresses are typically assigned using one of the following ranges:

• 10.0.0.0 to 10.255.255.255
• 172.16.0.0 to 172.31.255.255
• 192.168.0.0 to 192.168.255.255

These ranges are reserved for private use and are not assigned to any public devices. This means that devices within a private network can use these IP addresses to communicate with each other without fear of conflicts with other devices on the internet.

In order for a device in a private network to communicate with the internet, it must use a public IP address. This is typically done through a device called a router, which uses Network Address Translation (NAT) to map the private IP address of the device to a public IP address. This allows the device to communicate with the internet while still using a private IP address.

IP Address Classes

IP addresses are divided into classes to allow for the efficient use of IP addresses and to support the hierarchical structure of the internet. There are five classes of IP addresses: A, B, C, D, and E. Each class has a specific range of values and is intended for use in different types of networks.

• Class A: Class A addresses have a range of 1.0.0.0 to 126.0.0.0. They are intended for use in very large networks, such as those used by internet service providers (ISPs) or large corporations. Each class A network can support up to 16,777,214 hosts.
• Class B: Class B addresses have a range of 128.0.0.0 to 191.0.0.0. They are intended for use in medium-sized networks, such as those used by universities or large organizations. Each class B network can support up to 65,534 hosts.
• Class C: Class C addresses have a range of 192.0.0.0 to 223.0.0.0. They are intended for use in small networks, such as those used by small businesses or home networks. Each class C network can support up to 254 hosts.
• Class D: Class D addresses have a range of 224.0.0.0 to 239.0.0.0. They are reserved for multicast applications, which allow a single device to send data to multiple devices simultaneously.
• Class E: Class E addresses have a range of 240.0.0.0 to 254.0.0.0. They are reserved for experimental or future use and are not currently assigned to any devices.

In the past, the classes of IP addresses were used to determine the size of a network and the number of hosts it could support. However, with the depletion of IPv4 addresses, the use of classes has largely been replaced by the use of subnetting, which allows for a more efficient use of IP addresses.

OSI Model

The OSI model (Open Systems Interconnection model) is a framework for understanding how communications between different devices and systems take place over a network. It divides the process of communication into seven distinct layers, each of which represents a specific aspect of the communication process.

The seven layers of the OSI model are:

1. Physical: The physical layer is responsible for transmitting raw data over a physical medium, such as a copper wire or fiber optic cable. It includes the hardware components of the network, such as cables and connectors.
2. Data link: The data link layer is responsible for providing reliable communication over the physical layer. It includes protocols for error detection and correction, as well as for establishing and maintaining connections between devices.
3. Network: The network layer is responsible for routing data between devices on a network. It includes protocols for addressing, routing, and traffic management.
4. Transport: The transport layer is responsible for providing end-to-end communication between devices. It includes protocols for error recovery, flow control, and congestion control.
5. Session: The session layer is responsible for establishing, maintaining, and terminating connections between devices. It includes protocols for synchronizing communication and managing data exchange.
6. Presentation: The presentation layer is responsible for translating data into a format that can be understood by the application layer. It includes protocols for encoding, compression, and encryption.
7. Application: The application layer is the topmost layer of the OSI model and is responsible for providing the interface between the network and the application software running on the devices. It includes protocols for supporting specific applications, such as web browsing, email, and file transfer.

The OSI model is a useful reference for understanding how different devices and systems communicate with each other over a network. It is a widely accepted standard in the field of computer networking.

Packet Tracer

Packet Tracer is a network simulation software developed by Cisco Systems. It is primarily used for educational purposes to help students and professionals learn how to design, configure, and troubleshoot computer networks.

In Packet Tracer, users can create virtual networks using a variety of network devices, including routers, switches, and hubs. The software allows users to configure the devices and create a network topology, and then simulate the flow of data between devices. Packet Tracer also includes tools for analyzing network traffic and performance, and for troubleshooting network issues.

Packet Tracer is a valuable tool for learning about computer networking because it provides a hands-on, interactive learning environment that allows users to experiment and practice with different configurations and scenarios. It is widely used in computer science and engineering programs, as well as in professional training and certification programs for networking technologies.

Here is an example of how Packet Tracer can be used to set up a simple network:

1. Open Packet Tracer and create a new project.
2. Drag and drop a router, a switch, and two computers onto the workspace.
3. Connect the devices as follows:

• Connect the router to the switch using an Ethernet cable.
• Connect the computers to the switch using Ethernet cables.

Configure the router and switch by double-clicking on each device and going to the “Config” tab.

• On the router, set up a WAN connection and assign it a public IP address.
• On the switch, configure the port settings and assign each port a unique VLAN (Virtual LAN) number.

Configure the computers by double-clicking on each device and going to the “Config” tab.

• On each computer, configure the network settings and assign it a private IP address within the same subnet as the router.

Test the connectivity between the devices by pinging the IP addresses of the other devices.

This is a very simple example of how Packet Tracer can be used to set up a network. In a real-world scenario, the network would likely be more complex and include additional devices and configurations. Packet Tracer allows users to experiment with different configurations and troubleshoot any issues that may arise.