Topic 1: Network Troubleshooting

• Troubleshooting - refers to the process of identifying problems with a network through a rigorous and repeatable process and then solving those problems using testable methods.
• Basic Troubleshooting Steps

  1. Identify The Problem
  2. Develop a Theory
  3. Test the Theory
  4. Plan of Action
  5. Implement of the Solution
  6. Verify System Functionality
  7. Document the Issue
• Cable Problem - The cable which is used to connect two devices can get faulty, shortened or can be physically damaged.
• Connectivity Problem - The port or interface on which the device is connected or configured can be physically down or faulty due to which the source host will not be able to communicate with the destination host.
• Configuration Issue - Due to a wrong configuration, looping the IP, routing problem and other configuration issues, network fault may arise and the services will get affected.
• Software Issue - Owing to software compatibility issues and versions mismatch, the transmission of IP data packets between the source and destination is interrupted.
• Traffic Overload - If the link is over utilized then the capacity or traffic on a device is more than the carrying capacity of it and due to overload condition the device will start behaving abnormally.
• Network IP Issue - Due to improper configuration of IP addresses and subnet mask and routing IP to the next hop, the source will not be able to reach the destination IP through the network.
• On Windows PCs, the command prompt can be accessed by searching for it in the start menu or by typing “cmd” into the Run
• On a Linux system, you can press CTRL + ALT + T to open the command line.
• ping - A TCP/IP utility that transmits a datagram to another host, specified in the command. If the network is functioning properly, the receiving host returns the datagram.
• tracert - A TCP/IP utility that determines the route data takes to get to a particular destination. This tool can help you to determine where you are losing packets in the network, helping to identify
• nslookup - A DNS utility that displays the IP address of a hostname or vice versa. This tool is useful for identifying problems involving DNS name resolution.
• ipconfig - A Windows TCP/IP utility that verifies network settings and connections. It can tell you a host’s IP address, subnet mask and default gateway, alongside other important network information.
• arp - A utility that supports the service of the TCP/IP protocol suite. It lets the network admin view the cache and add or delete cache entries. It can be used to address problems having to do with specific connections between a workstation and a host.
• dig - A Linux or UNIX command-line tool that will display name server information. It can be used to troubleshoot problems in DNS name resolution.
• Packet Sniffer - Provides a comprehensive view of a given network. You can use this application to analyze traffic on the network, figure out which ports are open and identify network vulnerabilities.
• Port Scanner - Looks for open ports on the target device and gathers information, including whether the port is open or closed, what services are running on a given port and information about the operating system on that machine. This application can be used to figure out which ports are in use and identify points in a network that could be vulnerable to outside attacks.
• Protocol Analyzer - Integrates diagnostic and reporting capabilities to provide a comprehensive view of an organization's network. You can use analyzers to troubleshoot network problems and detect intrusions into your network.
• WI-FI Analyzer - Detects devices and points of interference in a WI-FI signal. This tool can help you to troubleshoot issues in network connectivity over a wireless network.
• Bandwidth Speed Tester - Tests the bandwidth and latency of a user’s internet connection. This application is typical accessed through a third-party website and can be used to confirm user reports about slow connections or download speeds.
• Wire Crimpers - is a tool that attaches media connectors to the ends of cables. You can use it to make or modify network cables.
• Cable Testers - is a tool that verifies if a signal is transmitted by a given cable. You can use one to find out whether the cables in your network are functioning properly when diagnosing connectivity issues.
• Punch Down Tool - is used in a wiring closet to connect cable wires directly to a patch panel or punch-down block. This tool makes it easier to connect wires than it would be to do it by hand.
• TDR - is a measuring tool that transmits an electrical pulse on a cable and measures the reflected signal. In a functioning cable, the signal does not reflect and is absorbed in the other end.
• OTDR - used for measuring fiber optic cables, which are becoming more common in modern networks.
• TDR stands for Time Domain Reflectometer
• OTDR stands for Optical Time Domain Reflectometer
• Light Meter - also known as optical power meters, are devices used to measure the power in an optical signal
• Tone Generator - is a device that sends an electrical signal through one pair of UTP wires.
• Tone Locator - is a device that emits an audible tone when it detects a signal in a pair of wires. You can use these tools to verify that signals are passing through the wires in your network. They are often used to confirm phone connectivity.
• Loopback Adapter - is a virtual or physical tool that can be used for troubleshooting network transmission issues. It can be used by utilizing a special connector that redirects the electrical signal back to the transmitting system.
• Multimeter - is an electronic instrument that takes electrical measurements such as voltage, current and resistance.
• Spectrum Analyzer - is an instrument that displays the variation of a signal strength against the frequency.
• ARP stands for Address Resolution Protocol
• TCP stands for Transmission Control Protocol
• UTP stands for Unshielded Twisted Pair