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Practice Exercise: Basic Computer Networking Lab using Linux nmap Command

Introduction

Welcome to the Basic Computer Networking Lab! In this lab, you will learn how to use the nmap command on a Linux server to effectively explore networking aspects, troubleshoot network issues, and perform security assessments. This hands-on lab is designed to help future Site Reliability Engineers (SREs) gain practical experience with nmap.

Prerequisites

Before you begin this lab, you should have the following:

  • Access to a Linux server (e.g., Ubuntu, CentOS) as your client
  • Basic knowledge of Linux command-line interface (CLI)
  • SSH access to the Linux server
  • Administrative privileges or sudo access on the server

Scenario

You are a future Site Reliability Engineer (SRE) responsible for ensuring the availability and security of online services. You will use your Linux server as a client to perform network scans and troubleshoot network issues. Additionally, you will use nmap to assess the security posture of your server and external websites.

Task 1: Basic Port Scan

Objective: Learn how to perform a basic port scan using nmap.

Procedure:

  1. Log in to your Linux server using SSH.
  2. Open a terminal window.
  3. Run the following command to perform a basic port scan on your server:

nmap localhost

  1. Analyze the output to identify open ports on your server.

Task 2: Service Version Detection

Objective: Learn how to use nmap to detect service versions running on open ports.

Procedure:

  1. Run the following command to perform a version detection scan on your server:

nmap -sV localhost

  1. Examine the output to identify services and their versions running on open ports.

Task 3: Scan Specific Ports

Objective: Learn how to specify specific ports to scan using nmap.

Procedure:

  1. Run the following command to scan only ports 80 and 443 on your server:

nmap -p 80,443 localhost

  1. Review the output to see if ports 80 and 443 are open.

Task 4: Scan Multiple Hosts

Objective: Learn how to use nmap to scan multiple hosts simultaneously.

Procedure:

  1. Run the following command to scan both your server (localhost) and a popular website (e.g., google.com):

nmap localhost google.com

  1. Analyze the output to identify open ports on your server and the website.

Task 5: Scan Target by IP Range

Objective: Learn how to scan a range of IP addresses using nmap.

Procedure:

  1. Run the following command to scan a range of IP addresses (e.g., 192.168.1.1-10):

nmap 192.168.1.1-10

Task 6: OS Detection

Objective: Learn how to use nmap for operating system detection.

Procedure:

  1. Run the following command to perform an OS detection scan on your server:

nmap -O localhost

  1. Review the output to identify the detected operating system.

Task 7: Scan with Firewall Evasion Techniques

Objective: Learn how to use nmap with firewall evasion techniques.

Procedure:

  1. Run the following command to perform an nmap scan with firewall evasion using the SYN/ACK scan technique:

nmap -sA localhost

  1. Examine the output for scan results and the evasion technique used.

Task 8: Perform a Fast Scan

Objective: Learn how to use nmap to perform a fast scan.

Procedure:

  1. Run the following command to perform a fast scan on your server:

nmap -F localhost

  1. Analyze the output to see which ports are open in the fast scan.

Task 9: Save Scan Results to a File

Objective: Learn how to save nmap scan results to a file.

Procedure:

  1. Run the following command to perform a scan and save the results to a file named "scan_results.txt":

nmap -oN scan_results.txt localhost

  1. Verify that the results have been saved to the "scan_results.txt" file.

Task 10: Troubleshooting Command

Objective: Learn how to use nmap to troubleshoot network connectivity issues.

Procedure:

  1. Imagine you are experiencing connectivity issues to an external web server (e.g., example.com). Run the following command to troubleshoot and diagnose connectivity problems:

nmap -p 80,443 example.com

  1. Analyze the nmap output to identify any issues with the target server's ports and services.

Congratulations! You've completed the Basic Computer Networking Lab using the nmap command. This hands-on experience will help you become proficient in using nmap for network scanning, troubleshooting, and security assessments.

Remember that nmap is a powerful tool that can provide valuable insights into network configurations and security vulnerabilities, so use it responsibly and ethically in your SRE role.