Network Troubleshooting Tools

Troubleshooting Tools Overview

Beyond basic diagnostics, a suite of free web-based and command line tools empowers network administrators and enthusiasts to delve deeper into network analysis and problem-solving. These tools offer advanced functionalities, aiding in the identification and resolution of complex network issues without the need for extensive software installations.

Key Functions

  • Advanced Network Diagnostics: Perform detailed network analysis, including packet analysis and security audits.

  • IP Address and Domain Analysis: Retrieve comprehensive information about IP addresses, domains, and their relationships.

  • DNS Record Analysis: Examine DNS records in detail, including propagation and security aspects.

  • Packet Loss and Jitter Analysis: Measure network performance metrics beyond simple latency.

  • SSL/TLS Certificate Analysis: Inspect SSL/TLS certificates for validity and security.

  • Inducing Paranoia:

  • Inducing More Paranoia:

Common Web-Based Tools and Their Advanced Features

  • IP Address Check:
    • What Is My IP Address?: displays your public IP address and related information, such as your location and ISP.
    • ifconfig: Helps users find their IP address and other connection-related information.
  • DNS Record Analysis:
    • DNSViz: Visualizes DNSSEC records and identifies potential security issues.
    • MXToolbox: Offers comprehensive DNS checks, including MX records, SPF records, and blacklist checks.
  • Packet Loss, Jitter Analysis, & Speed Test :
    • Cloudflare: Provides detailed speed tests and latency analysis, with a focus on consistent performance.
    • Speedtest by Ookla: Measures your internet connection’s performance, providing data on download and upload speeds, as well as latency (ping).
  • SSL/TLS Certificate Analysis:

Basic Network Commands

These commands are essential tools for diagnosing and troubleshooting network issues. Understanding their usage and options can significantly improve your network troubleshooting skills.

ping

  • Purpose: Tests basic network connectivity to a specified host.
  • Usage:
    • ping <hostname or IP address>
    • Example: ping google.com or ping 192.168.1.1
  • Linux/macOS Options:
    • -c <count>: Sends a specified number of packets.
    • -i <interval>: Sets the interval between packets.
    • -t: ping until interrupted.
  • Windows Options:
    • -t: Pings the specified host until interrupted.
    • -n <count>: Sends a specified number of echo requests.
    • -l <size>: Sends echo requests with the specified buffer size.

traceroute / tracert

  • Purpose: Traces the route packets take to a destination, showing each hop along the way.
  • Usage:
    • traceroute <hostname or IP address> (Linux/macOS)
    • tracert <hostname or IP address> (Windows)
    • Example: traceroute google.com or tracert 8.8.8.8

ipconfig / ifconfig

  • Purpose: Displays network interface configuration information.
  • Usage:
    • ipconfig (Windows)
    • ifconfig (Linux/macOS)
  • Windows Options:
    • /all: Displays detailed configuration information.
    • /release: Releases the IP address.
    • /renew: Renews the IP address.
    • /flushdns: Clears the DNS resolver cache.
  • Linux/macOS Options:
    • <interface>: Specifies the interface to display.
    • up/down: Enables/disables an interface.

nslookup

  • Purpose: Queries DNS servers to resolve hostnames to IP addresses and vice versa.
  • Usage:
    • nslookup <hostname or IP address>
    • Example: nslookup google.com or nslookup 8.8.8.8
  • Can also be used in interactive mode by just typing nslookup.

arp

  • Purpose: Displays and modifies the Address Resolution Protocol (ARP) cache, which maps IP addresses to MAC addresses.
  • Usage:
    • arp -a (Displays the ARP cache)
    • arp -d <IP address> (Deletes an entry from the ARP cache)
  • Windows Options:
    • -s <IP address> <MAC address> (Adds a static entry to the ARP cache).
  • Linux/macOS Options:
    • -d <IP address> : Delete an entry.

netstat

  • Purpose: Displays network connections, routing tables, and network interface statistics.
  • Usage:
    • netstat
  • Linux/macOS Options:
    • -a: Displays all connections and listening ports.
    • -n: Displays addresses and port numbers in numerical form.
    • -t: Displays TCP connections.
    • -u: Displays UDP connections.
    • -l: Displays listening ports.
    • -p: Displays the process ID and name associated with each connection.
  • Windows Options:
    • -a: Displays all connections and listening ports.
    • -n: Displays addresses and port numbers in numerical form.
    • -o: Displays the process ID associated with each connection.
    • -b: Displays the executable involved in creating each connection or listening port.

dig

  • Linux/macOS
  • Purpose: A more advanced DNS lookup utility than nslookup.
  • Usage:
    • dig <hostname> <record type>
    • Example: dig google.com A or dig example.com MX
  • Common record types: A, AAAA, CNAME, MX, TXT, NS.

tcpdump

  • Linux/macOS
  • Purpose: A powerful command-line packet analyzer.
  • Usage:
    • tcpdump -i <interface> <filter>
    • Example: tcpdump -i eth0 port 80 or tcpdump -i any icmp
  • Requires root privileges.

pathping

  • Windows
  • Purpose: Combines ping and traceroute to provide detailed information about network latency and packet loss along a route.
  • Usage:
    • pathping <destination>
    • Example: pathping google.com

mtr

  • Linux/macOS
  • Purpose: Combines the functionality of ping and traceroute in a single tool, providing real-time network path analysis.
  • Usage:
    • mtr <destination>
    • Example: mtr google.com

route

  • Purpose: Displays and modifies the IP routing table.
  • Usage:
    • route (Linux/macOS)
    • route print (Windows)
  • Linux/macOS Options:
    • add: Adds a route.
    • del: Deletes a route.
  • Windows Options:
    • add: Adds a route.
    • delete: Deletes a route.

hostname

  • Purpose: Displays or sets the hostname of the system.
  • Usage:
    • hostname

ssh

  • Linux/macOS/Windows - via OpenSSH
  • Purpose: Securely connects to a remote system.
  • Usage:

curl

  • Linux/macOS/Windows
  • Purpose: Transfers data from or to a server using various protocols (HTTP, HTTPS, FTP, etc.).
  • Usage:
    • curl <URL>
    • Example: curl https://google.com

wget

  • Linux/macOS/Windows - via Windows Subsystem for Linux or similar
  • Purpose: Retrieves files from web servers.
  • Usage:
    • wget <URL>
    • Example: wget https://example.com/file.zip

Advanced Usage Tips

  • Interpret Complex Data: Learn to interpret advanced network data, such as packet captures and DNSSEC records.
  • Automate Tests: Use scripting or browser extensions to automate repetitive network tests.
  • Combine Tools for Comprehensive Analysis: Use multiple tools in conjunction to gain a holistic view of network issues.
  • Stay Updated: Network technologies and security threats are constantly evolving, so stay updated on the latest tools and techniques.
  • Understand Limitations: While web-based tools are convenient, they may have limitations compared to dedicated software.
  • Use caution: when using tools that scan external networks, make sure you are not violating any terms of service or laws.

Further Reading