In the world of system administration, ensuring that your network connections are functioning correctly is crucial. Connectivity tests help you diagnose and troubleshoot network issues, ensuring that your systems can communicate effectively. This article will guide you through the process of performing connectivity tests in a Linux environment using various tools and commands. These tests are essential for maintaining network integrity, diagnosing issues, and ensuring smooth operation of your systems.

Examples:

1. Ping Command: The ping command is one of the most basic and widely used tools for connectivity testing. It sends ICMP echo requests to a specified host and waits for a reply.

   ping -c 4 google.com

   This command sends 4 ICMP echo requests to google.com. The -c option specifies the number of packets to send.

2. Traceroute Command: The traceroute command is used to trace the path that packets take to reach a destination. It helps in identifying where the connection is slowing down or failing.

   traceroute google.com

   This command will display the route packets take to reach google.com, showing each hop along the way.

3. Netcat (nc) Command: Netcat is a versatile networking tool that can be used for various connectivity tests, including port scanning and checking open ports.

   nc -zv google.com 80

   This command checks if port 80 (HTTP) on google.com is open. The -z option is used for scanning without sending data, and -v enables verbose mode.

4. Telnet Command: The telnet command can be used to test connectivity to a specific port on a remote host.

   telnet google.com 80

   This command attempts to connect to port 80 on google.com. If the connection is successful, it indicates that the port is open and accessible.

5. Curl Command: The curl command is useful for testing HTTP/HTTPS connectivity and retrieving web content.

   curl -I https://www.google.com

   This command fetches the HTTP headers from google.com, indicating whether the site is reachable and providing additional information about the response.

6. MTR Command: MTR (My Traceroute) combines the functionality of ping and traceroute to provide a more detailed view of network performance.

   mtr google.com

   This command provides a continuous traceroute, showing the latency and packet loss at each hop.