4.Ping-pong:A simple tool to check network connectivity,free and easy to use.

Based on your thought process and considerations, here is a curated list of free network tools that you can use, along with a brief explanation of each:

1. Wireshark: A powerful network traffic analyzer that helps monitor and troubleshoot network traffic. It is free and open-source, ideal for detailed network traffic analysis.

2. OpenVPN: A free and open-source remote access tool that allows connecting to a remote server over an unreliable internet connection. It is suitable for personal or small business use.

3. ipconfig: Provides information about your IP addresses and network connections, available for free and part of the system information toolchain.

4. Snort: A network monitoring tool that offers advanced features like network segmentation and firewall monitoring, available for free but may require a subscription for full functionality.

5. Zero Trust: A free network security tool that helps prevent unauthorized access, requiring a subscription for advanced features.

6. FTTP: A free internet telephony tool for connecting to an internet connection via a phone, with limitations on simultaneous connections.

7. BGP: A protocol for routing data in a network, free and open-source, suitable for basic networking needs.

8. Wireshark: As mentioned earlier, this tool is available, but it's noted for its advanced features despite being free.

9. Netflow: Likely part of a paid service for professional networks, but available for students or small businesses. Check licensing details before use.

Each tool has its own requirements and use cases, so it's important to verify availability, licensing, and compatibility with your operating system. Consider the ease of use, usability, and available documentation for each tool to determine the best fit for your needs.