Cabling Connectivity Issues

Common networking issues

Attenuation

• Attenuation is the lost of signal over distance.

• Causes packet loss.

• Implementing a repeater to regenerate the signal.

Interference

• Usually caused  by Electromagnetic Interference (EMI).

• Also known as crosstalk.

• Improper installation of networking cables.

• Affects wireless networks where there are multiple devices generating a signal on the same frequency.

Decibel (dB) loss

• This is the loss of signal.

• Can be caused by the following:

  • Interference

  • Dirty cables that has dust or dirty on the connectors.

  • Damaged cable.

Incorrect pinout / Transmit and receive (TX/RX) reversed

• The pinout within a copper cable is made incorrectly.

• Can cause the transmitting and receiving pins to be reversed.

Bad ports / Incorrect transceivers

• The physical interfaces / ports on a device may be faulty.

• Ensure the transceiver supports the cable type.

Light-emitting diode (LED) status indicators

• The status lights on a device can help determine whether an issue exists or not.

Duplexing issues

• Duplex mismatch creates latency and packet loss issues.

Networking Tools

Making Cables

• Snips/cutters - Used for cutting wires.

• Cable stripper - Used to strip the outer coating of the wire.

• Cable crimper - Used to push the gold pins of the RJ-45 jack down to meet the copper wires.

• Punchdown tool - Used to push down / terminate the copper wires onto a keystone, 66 blocks and 110 blocks.

• Fusion splicers - Used to join fiber optic cables.

Testing Cables

• Multimeter - Test current, voltage and resistance.

• Cable tester - Test a network cable to determine if the wire map is made correctly.

• Tone generator - Allows you to physically trace cable between two point/places.

• Loopback adapter - Used to test network connectivity on a system that is isolated from a traditional network.

• Optical time-domain reflectometer (OTDR) - Used to test whether there is a breakage on a fiber optic cable.

• Fiber light meter - Used to test the strength of the light on a fiber optic cable.

Additional tools

• Tap - Usually a hardware-based device which allows a network professional to tap into a network connection to capture network traffic.

• Spectrum analyzers - Allows network professionals to determine whether any wireless signal interference exists within the vicinity.

• Crossover cables - Used to connect same devices together.

• Power over Ethernet - Allows switches to emit electrical current outbound from a switch port to the network cable to a device that supports PoE.

• Rollover cable/console cable - A special cable to used to connect to a Cisco device for out-of-band management.