Troubleshooting Tools Facts Flashcards
Loopback plug
A loopback plug, or loopback adapter, reflects a signal from the transmit port on a device to the receive port on the same device. Use the loopback plug to verify that a device can both send and receive signals.
There are loopback plugs for both copper and fiber connections.
A failure in the loopback test indicates a faulty network card.
A successful loopback test means the problem is in the network cabling or another connectivity device.
You can purchase pre-made loopback plugs, or you can make an inexpensive one by cutting the end of a cable and manually connecting the transmit wires to the receive wires. To do this, connect the wire from pin 1 to the wire at pin 3, and the wire at pin 2 to the wire at pin 6.
Smartjack
A smartjack is an intelligent loopback device installed at the demarcation point for a WAN service. Key points are:
Technicians at the central office can send diagnostic commands to the smartjack to test connectivity and performance between the central office and the demarc.
When you contact a WAN service provider for assistance, the provider might execute a test using the smartjack.
A successful test indicates that the problem is within the customer premises equipment (CPE).
Known good spares
One valuable troubleshooting method is to keep a set of components that you know are in proper functioning order. If you suspect a problem in a component, swap it with the known good component. If the problem is not resolved, troubleshoot other components. Examples of using this strategy include the following:
Change the drop cable that connects a computer to the network.
Replace a NIC with a verified working NIC.
Move a device from one switch port to another.
Cable tester
A cable tester (line tester) verifies that the cable can carry a signal from one end to the other and that all wires are in the correct positions.
High-end cable testers can check for various miswire conditions such as wire mapping, reversals, split pairs, shorts, or open circuits.
You can use a cable tester to quickly identify a crossover and a straight-through cable.
Most testers have a single unit that tests both ends of the cable at once.
Many testers come with a second unit that can be plugged into one end of a long cable run to test the entire cable.
Time-domain reflectometer
(TDR)
A time-domain reflectometer is a special device that sends electrical pulses on a wire to discover information about the cable. The TDR measures impedance discontinuities (the echo received on wire in response to a signal on the same wire). The results of this test can be used to identify several variables:
Estimated wire length.
Cable impedance.
The location of splices and connectors on the wire.
The location of shorts and open circuits.
Optical time-domain reflectometer
(OTDR)
An optical time-domain reflector performs the same function as a TDR, but is used for fiber optic cables. An OTDR sends light pulses into the fiber cable and measures the light that is scattered or reflected back to the device. The information is then used to identify specifics about the cable:
The location of a break.
Estimated cable length.
Signal attenuation (loss) over the length of the cable.
Cable certifier
A cable certifier is a multi-function tool that verifies that a cable or an installation meets the requirements for a specific architecture implementation. For example, you would use a certifier to verify that a specific drop cable meets the specifications for 1000BaseT networking.
A certifier is very important for Cat 6 cable used with bandwidths at or above 1000 Mbps. Slight errors in connectors or wires can cause the network to function at 100 Mbps instead of the desired 1000 Mbps (10 Gbps).
Certifiers can also validate the bandwidth capabilities of network interface cards and switches. Many can detect the duplex settings of network devices.
Most certifiers include features of a toner probe, TDR, and cable tester.
Certifiers are very expensive and are typically used by organizations that specialize in wiring installations.
Toner probe
A toner probe is composed of two devices used together to trace the end of a wire from a known endpoint to the termination point in the wiring closet. To use a toner probe:
Connect the tone generator to one end of the wire. It will send a signal on the wire.
In the wiring closet, touch the probe to wires or place the probe close to wires. A sound at the probe indicates that the generated tone has been detected and the wire that you are touching is the termination point for the wire you are tracing.
Multimeter
A multimeter is a device used to test various electrical properties. A multimeter can measure several parameters:
AC and DC voltage
Current (amps)
Resistance (ohms)
Capacitance
Frequency
Voltage event recorder
A voltage event recorder tracks voltage conditions on a power line. Basic recorders track only undervoltage or overvoltage conditions. More advanced devices track conditions over time and create a graph, saving data from a program running on a computer.
Some UPS systems include a simple voltage event recorder. Use a voltage event recorder to identify periods of low or high voltage that can adversely affect network components.
Environmental monitor
An environmental monitor does what its name implies, it monitors the environmental conditions of a specific area or device.
Monitors are often used to track the conditions within server rooms, such as temperature, humidity, water, smoke, motion, and air flow.
Typically, computers (especially servers) have an internal monitor that measures fan speed and CPU temperature.
Many monitors sound an alarm if a specified temperature or other environmental condition is reached.
Wire stripper, snips, and crimpers
Wire strippers remove the protective sheath of a cable in order to expose the conductive wire.
Wire strippers are rated to specific gauge (cable width) ranges.
Most wire strippers are combination tools. They can strip, cut, and crimp cables.
Almost all wire strippers have multiple holes or can be adjusted for specific cable sizes.
A crimping tool is used to attach connectors to wires. Some crimpers are designed for power connections. A special crimper is used to attach RJ45 connectors to twisted pair cables.
Snips are cutting tools used to cut cables or wires to a specific length or to remove damaged sections. A diagonal cutter is an example of a snip tool.
Whenever possible, use a wire stripper instead of snips to strip a cable. Wire strippers are specifically designed to cut only the protective sheath without cutting the internal wire.
Speed test website
A speed test website is an online tool that is used to test the bandwidth of the internet connection. There are countless speed test websites available, all of them provide essentially the same information:
Connection latency (ping)
Download speed
Upload speed
Fusion splicer
A fusion splicer is a tool that uses heat to join two optical fibers together. It fuses them together end-to-end. This is done in situations when the cable is broken or too short for the purpose it’s being used for.
The fusion splicer ensures that the two cables are fused together in an accurate and precise way to eliminate (as much as possible) any light being scattered or reflected back by the splice. The source of heat used by the fusion splicer is usually an electric arc, but could also be a laser, a gas flame, or a tungsten filament through which current is passed.
