The combination of different external software and modules improve the abilities of GNS3 in an effective manner even though it already serves as an environment for network simulation. On the basis of GNS3, we explore several major modules and elements, and offer descriptions for every aspect in an explicit way:

1. Dynamips

• Description: Particularly, Dynamips simulates Cisco IOS routers and is considered as a novel module in which the GNS3 was constructed. To simulate arrangements of Cisco router and test network topologies, this module enables users. For facilitating the training of IOS commands and arrangement settings, it aids a wide array of Cisco IOS images.

2. IOU (IOS on Unix) / IOL (IOS on Linux)

• Description: Exactly on a Unix or Linux operating system, the execution of Cisco IOS is facilitated by IOU/IOL that is examined as copyrighted software. For simulating Cisco routers and switches without the requirement for any real IOS images, GNS3 employs IOL/IOU. As the conventional Dynamips has challenges in the process of simulating Cisco switches, it is specifically effective and helpful for switching labs.

3. QEMU (Quick Emulator)

• Description: To execute operating system and appliance images like PIX, IPS/IDS, and ASA, GNS3 utilizes QEMU that is referred to as an openly-available and common machine emulator and virtualizer. Diverse frameworks such as ARM, x86, and x86_64 (AMD64/Intel64) are assisted by QEMU. It also enables the process of emulating non-Cisco devices.

4. VirtualBox and VMware Integration

• Description: Users are enabled to encompass virtual machines (VMs) into their network topologies by the combination of GNS3 with VMware and VirtualBox. To offer a highly extensive network testing platform, it is certainly very helpful for the process of simulating clients, network appliances which are accessible as VM images, or servers.

5. VPCS (Virtual PC Simulator)

• Description: To simulate by a maximum of nine PCs on a network, users are allowed by this VPCS that is known as a basic PC simulator. For appending server or client nodes to a network topology, it is considered as a lightweight choice because it can be more effective in testing traceroute, DHCP operations, and ping without the requirement for completely developed VMs.

6. Wireshark

• Description: On the virtual platforms that are developed in GNS3, users are enabled to seize and examine packets by the combination of Wireshark. Based on the traffic that is flowing across the network, it provides perceptions. For the objective of troubleshooting, protocol analysis, and education, this is highly crucial.

7. Solar-PuTTY / SuperPuTTY

• Description: In order to approach the network devices’ command line interface (CLI), GNS3 combines into terminal emulator programs such as SuperPuTTY and Solar-PuTTY. The process of handling several devices becomes more user-friendly because these tools offer tabbed SSH and Telnet client interfaces.

8. GNS3 VM

• Description: Specifically, when utilizing VirtualBox VMs or QEMU, GNS3 VM is suggested to execute CPU-intensive emulations. It is referred to as a virtual machine which is combined into the GNS3 client. When compared to executing all the processes exactly on the host OS, there is a chance to obtain greater stability and performance by hosting the GNS3 server element on the GNS3 VM.

9. Cloud Nodes

• Description: For linking your GNS3 topologies to the internet or actual networks, cloud nodes in GNS3 are highly utilized. By integrating with exterior networks, this module enables to simulate more practical network platforms.

10. Ethernet Switch and Frame Relay, ATM Switch

• Description: To simulate network segments, these modules are examined as more helpful and provide fundamental Layer 2 switching capabilities into GNS3. For specific network topologies, they offer essential abilities even though they are not having many characteristics like IOU/IOL for switching.

Why do we need network simulator?

Network simulators play a crucial role by offering various tools for modeling and simulation processes. It is majorly considered for academic, research, and other significant purposes. The following are numerous important reasons based on the requirements for network simulators:

1. Cost-Effectiveness

Specifically, when the network needs diverse devices and arrangements, constructing a physical network for the objective of testing, education, or exploration is generally cost-intensive. But, the experimentation with networks becomes more user-friendly because of the utilization of simulators that enable the simulation of complicated networks excluding the requirements for hardware sources. 

2. Scalability and Flexibility

Arranging extensive physical networks might be unrealistic or unattainable because of some logical basis, expense, or space. But the simulators facilitate the designing of extensive networks. For investigating different arrangements and settings without any physical conditions, users are capable of extending or changing their network topology in a simple manner with some limited processes. 

3. Safe Environment for Experimentation

Without causing any vulnerability to actual networks or data loss, network simulators enable the users to carry out testing processes with various arrangements, situations, and network protocols along with troubleshooting approaches and malicious assaults by offering a sandbox platform. 

4. Reproducibility

There is a possibility to save, distribute, and accurately recreate the experiments that are carried out in a simulated platform. For academic exploration or for situations in which an arrangement requires to undergo several testing processes based on the similar constraints for verifying the outcomes, this reproducibility approach is most significant. 

5. Rapid Prototyping and Testing

Before carrying out the implementation process in a real platform, simulators enable to model and test protocols, novel mechanisms, and network arrangements in a rapid manner. The resources and time that are needed for the process of creation and testing can be majorly minimized through the usage of simulators. 

6. Education and Training

Network simulators are considered as very useful tools for academic objectives. Without any requirement for high-valued lab arrangements, these tools enable students to gain knowledge in a practical way based on networking principles, network management approaches, and protocols. Certification candidates are also allowed to train on realistic situations that might be confronted by them in exams.   

7. Research and Development

In terms of a vast amount of constraints, researchers examine the efficiency of networking protocols, frameworks, and methods by utilizing network simulators. For offering perceptions which direct the creation of network solutions that are highly powerful and effective, simulators are capable of designing different aspects such as packet loss rates, network latency, and traffic loads. 

8. Support for Advanced Technologies

Particularly for the latest networking principles and mechanisms that might not be currently accessible in physical design in a broader manner, simulators encompass assistance efficiently. To investigate and acquire knowledge based on current networking-related developments like Network Functions Virtualization (NFV), future internet protocols, and Software-Defined Networking (SDN), simulators enable users.  

9. Analysis and Optimization

To assist in detecting obstructions, enhancing network efficiency, and strengthening traffic flow, network simulators mostly include analysis tools. For confirming that the networks are modeled with greatest strength and effectiveness, they have the ability to simulate diverse constraints. 

10. Integration and Compatibility Testing

For assuring seamless combination and compatibility into latest network frameworks, the simulators allow to test in what way novel protocols or devices communicate with previous systems.