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:
  • DigiCert SSL Installation Diagnostics Tool: Checks the installation of SSL certificates and identifies potential issues.

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:
  • ssh <username>@<hostname or IP address>
  • Example: ssh [email protected]

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

• Networking Tips & Tricks

Routers

Routers Overview

Routers are essential networking devices that forward data packets between computer networks. They play a crucial role in connecting local networks to the internet and managing network traffic.

Key Functions

• Packet Forwarding: Routers determine the best path for data packets to travel across networks.
• Network Address Translation (NAT): Routers translate private IP addresses to public IP addresses, allowing multiple devices on a local network to share a single internet connection.
• Firewall Functionality: Many routers include built-in firewall features to protect networks from unauthorized access.
• Routing Protocols: Routers use routing protocols (e.g., OSPF, BGP) to exchange routing information with other routers.

Common Router Types

• Home Routers: Designed for small home networks.
• Small Business Routers: Offer more advanced features for small businesses.
• Enterprise Routers: High-performance routers for large organizations.
• Core Routers: High-capacity routers used in the internet backbone.

Configuration Basics

To configure a router, you typically access its web-based interface or use a command-line interface (CLI). Common configuration tasks include:

• Setting the router’s IP address.
• Configuring DHCP settings.
• Setting up port forwarding.
• Configuring wireless settings (if applicable).

Further Reading

• How Routers Work

Switches

Switches Overview

Switches are networking devices that connect devices within a local area network (LAN). They intelligently forward data packets to specific devices based on their MAC addresses, improving network efficiency.

Key Functions

• MAC Address Learning: Switches learn the MAC addresses of connected devices and store them in a MAC address table.
• Packet Forwarding: Switches forward data packets only to the intended destination device, reducing network congestion.
• VLAN Support: Many switches support virtual LANs (VLANs), allowing you to segment a physical network into multiple logical networks.
• Spanning Tree Protocol (STP): STP prevents network loops, which can cause broadcast storms and network instability.

Common Switch Types

• Unmanaged Switches: Simple plug-and-play switches with no configuration options.
• Managed Switches: Offer advanced features, such as VLANs, STP, and quality of service (QoS).
• PoE Switches: Power over Ethernet (PoE) switches provide power to connected devices, such as IP phones and wireless access points.
• Layer 3 Switches: Combine the functions of a switch and a router, allowing for routing between VLANs.

Configuration Basics

Managed switches typically have a web-based interface or a command-line interface (CLI) for configuration. Common configuration tasks include:

• Configuring VLANs.
• Setting up STP.
• Enabling QoS.
• Monitoring network traffic.
• Configuring PoE (if applicable).

Further Reading

• How Network Switches Work

Firewalls

Firewalls Overview

Firewalls are essential network security devices that monitor and control incoming and outgoing network traffic based on predefined security rules. They act as a barrier between trusted internal networks and untrusted external networks, such as the internet.

Key Functions

• Packet Filtering: Firewalls examine network packets and allow or block them based on source and destination IP addresses, ports, and protocols.
• Stateful Inspection: Stateful firewalls track the state of network connections and allow only legitimate traffic to pass through.
• Network Address Translation (NAT): Many firewalls include NAT functionality to translate private IP addresses to public IP addresses.
• Intrusion Prevention System (IPS): Some firewalls include IPS capabilities to detect and block malicious network traffic.
• VPN Support: Many firewalls support virtual private networks (VPNs) to provide secure remote access.

Common Firewall Types

• Hardware Firewalls: Dedicated physical devices that provide high-performance firewall protection.
• Software Firewalls: Software applications installed on computers or servers.
• Next-Generation Firewalls (NGFWs): Advanced firewalls that include features such as application control, intrusion prevention, and deep packet inspection.

Configuration Basics

Firewall configuration typically involves defining security rules that specify which traffic is allowed or blocked. Common configuration tasks include:

• Setting up access control lists (ACLs).
• Configuring NAT rules.
• Enabling intrusion detection and prevention.
• Setting up VPN connections.
• Managing firewall logs.

Further Reading

• How Firewalls Work

Modems

Modems Overview

Modems are networking devices that convert digital signals from your computer or network into analog signals that can be transmitted over telephone lines, cable lines, or fiber optic cables. They also convert incoming analog signals back into digital signals. Modems are essential for connecting to the internet.

Key Functions

• Signal Modulation: Modems modulate digital signals into analog signals for transmission.
• Signal Demodulation: Modems demodulate incoming analog signals back into digital signals.
• Internet Connectivity: Modems provide the physical connection to your Internet Service Provider (ISP).
• Bridging: Some modems also perform bridging functions, connecting your local network to the ISP’s network.

Common Modem Types

• Cable Modems: Used with cable internet services.
• DSL Modems: Used with digital subscriber line (DSL) internet services.
• Fiber Modems (ONTs): Used with fiber optic internet services.
• Dial-up Modems: Older modems used with traditional telephone lines.
• Cellular Modems: Uses cellular networks for internet access.

Configuration Basics

Modem configuration is often handled automatically by your ISP. However, some common configuration tasks may include:

• MAC Address Cloning: In some cases, you may need to clone the MAC address of a previous device.
• Bridge Mode: Configuring the modem to bridge mode disables its routing functions, allowing a separate router to handle network traffic.
• Firmware Updates: Keeping the modem’s firmware up to date is important for performance and security.
• Connecting to the router: Connecting the modem to a router is usually done via an ethernet cable.

Further Reading

• How Modems Work

Wireless Access Points

Wireless Access Points Overview

Wireless Access Points (WAPs) are networking devices that create a Wireless Local Area Network (WLAN), allowing Wi-Fi enabled devices to connect to a wired network. They are essential for extending network connectivity wirelessly throughout a home, office, or public space.

Key Functions

• Wireless Connectivity: Provides Wi-Fi access for devices within range.
• Network Extension: Extends the reach of a wired network wirelessly.
• Data Transmission: Transmits and receives data over wireless frequencies.
• Security: Implements security protocols to protect the wireless network.

Common WAP Types

• Standalone Access Points: Single devices that provide wireless connectivity.
• Mesh Wi-Fi Systems: Multiple interconnected units that create a seamless wireless network.
• Wireless Routers (with AP functionality): Devices that combine routing and access point functions.
• Outdoor Access Points: Weather-resistant devices designed for outdoor use.
• Ceiling Mounted Access Points: Designed for optimal coverage when mounted on a ceiling.

Configuration Basics

WAP configuration can vary depending on the device, but common tasks include:

• SSID (Network Name) Configuration: Setting the name of the wireless network.
• Security Protocol Configuration: Selecting and configuring security protocols (e.g., WPA2/WPA3).
• Password Configuration: Setting a strong password for the wireless network.
• Channel Selection: Choosing an optimal Wi-Fi channel to minimize interference.
• Firmware Updates: Keeping the WAP’s firmware up to date for performance and security.
• IP Address Configuration: Setting a static or dynamic IP address for the WAP.
• Connecting to the network: Connecting the access point to a router or switch via an ethernet cable.

Further Reading

• How Wireless Access Points Work
• Understanding Wi-Fi Channels

emailchecker

A simple command-line tool to classify email domains as “Free Domain” or “Business Domain”.

📥 Download

Download emailchecker Here

⚡ How to Use

1️⃣ Prepare Your Input

• Create a CSV file named emails.csv with a single column labeled “Emails”.
• Place emails.csv in the same directory as emailchecker.exe.

2️⃣ Run the Application

• Double-click emailchecker.exe to start processing.

3️⃣ View the Output

• A folder named “Output” will be created in the same directory.
• Inside Output/, find classified_emails.csv, which contains the email list with a new “Domain Type” column.

📂 Folder Structure

Application Directory/
│── emailchecker.exe
│── emails.csv
│── Output/
│── repo/

📋 Built-in Data

• The tool includes a list of free email domains in repo/freeDomains.csv.
• Modify this file to customize the free domain list.

✏️ Example Files

Example emails.csv:

Example classified_emails.csv Output:

📊 Example Classified Emails Table

⚠️ Important Notes

✅ emails.csv must be in the same directory as the executable.
✅ The output file will always be placed in the “Output” folder.

📧 Contact

For questions or issues, contact: [email protected]