Network Diagnostics

Learning Objectives

• Understand core networking concepts: IP addressing, DNS, routing
• Learn to troubleshoot network connectivity issues
• Develop skills in network performance analysis
• Interpret diagnostic tool outputs
• Create reusable network troubleshooting scripts

Requirements

You are required to write a script network-diagnostics.sh that accepts a hostname or IP address and performs comprehensive network diagnostics:

1. Connection Testing
   • Validate input format (hostname or IP)
   • Perform ICMP ping test with configurable count and packet size
   • Report packet loss percentage and RTT statistics (min/avg/max)
   • Test connection to common ports (80, 443, 22)
2. Routing Analysis
   • Run traceroute to the target
   • Count number of hops to destination
   • Calculate latency per hop
   • Detect routing anomalies (timeouts, high latency hops)
3. DNS Investigation
   • Forward and reverse DNS lookups
   • Query record types: A, AAAA, MX, TXT, CNAME
   • Check DNS resolution speed
   • Display TTL values
4. Network Information
   • Display local network configuration
   • Show active interfaces and their status
   • Display routing table
   • List established connections related to target
5. Reporting
   • Formatted, timestamped report
   • Summary section with pass/fail indicators
   • Save results to a structured log file
   • Recommend potential solutions for identified issues

Stretch Goals

• Add TLS/SSL certificate verification for HTTPS endpoints
• Implement parallel testing for faster results
• Add MTU discovery and path MTU testing
• Create ASCII visualizations of test results

Deliverables

• network-diagnostics.sh script
• Sample outputs for different test scenarios
• Documentation covering usage, result interpretation, and troubleshooting recommendations

References

• Linux Networking Commands
• DNS Concepts - Cloudflare
• Understanding traceroute
• Network Troubleshooting - Red Hat
• Netcat Guide - DigitalOcean

Once you complete this task you will know how to use command-line tools to diagnose network issues and interpret their outputs - crucial skills for operating distributed systems where network problems are the most common failure point.