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1.0 Networking Fundamentals

2.0 Network Implementations

3.0 Network Operations

4.0 Network Security

5.0 Network Troubleshooting

Practice Tests Overview

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5.0 Network Troubleshooting

5.4 Given a scenario, troubleshoot common wireless connectivity issues

Wireless networks only add to the overall pile of problems of cabling.

Makiel [Muh-Keel]

Last edited 544 days ago by Makiel [Muh-Keel]

Wireless Performance can vary quite a bit due to a number of factors: interference, obstacles in the way, thick walls, and the # of people connected to the wifi, just to name a few.

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Specifications\Limitations of Wireless Signals

Throughput

Throughput Is the measure of the amount of data successfully transferred through a wireless network. You can measure this performance to get a realistic baseline of just how much data the wireless network is actually transmitting.

This metric will decrease as you add more devices to your wireless network.

Speed

Speed is the textbook maximum bandwidth available given by the ISP. Normally, the closer you get to the AP Antennas, the faster it becomes.

Distance

Distance is important when dealing with wi-fi as well. If a host device is too far from any AP antennas, the speed and throughput will increase/decrease proportional to it’s proximity to them.

Good rule of thumb is to be as close to the AP antennas as possible.

RSSI (Received Signal Strength Indication)

RSSI is the measure of a single radio signal received by a device on the wireless network.

Measured in decibel-milliwatts (dBm) and the closer you get to zero is better.

Ex. -50dbm is excellent while -80dbm is very poor

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EIRP (Effective isotropic radiated power)

EIRP is a metric value representing how strong the wireless AP is transmitting radio signals to any hosts connected to it’s Wi-Fi.

Signal Strength of signals being sent from the AP itself.

This transmission power is regulated by the FCC.

This metric is sometimes configurable on the AP itself. Always check and see if that’s an option.

EIRP Value equals (Transmit strength + antenna gain) - cable loss

Considerations when troubleshooting Wireless networks

Antennas

Antennas should be placed strategically throughout the site to ensure significant coverage.

Omnidirectional Antennas are the go-to choice for most environments.

Signal is evenly distributed on all sides

Coverage is projected in all directions

Only downside is you can’t focus the signal in one direction.

Directional Antennas allow use to focus the signal in one direction.

Best choice if you want to increase the power of the wireless signal

Used most of the time to bridge a gap and connect wireless networks between different buildings

Antenna/AP Placement

The best place to put an AP and/or its antenna is as close to the center of your wireless network as possible so it can reach as many devices as possible. You can also use third-party tools like the packet sniffers Wireshark and AirMagnet on a laptop to survey the site and establish how far your APs are actually transmitting.

Placement is important because poor placement can lead to interference and poor performance, or even no performance at all.

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Antenna Polarization

Polarization is the orientation of the antenna as its relative to the earth. Also known as the antenna’s physical alignment.

When setting up antennas be sure to make sure the transmitter antenna and the receiver antenna have the exact same polarization.

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AP association time

AP association time is the time it takes for a host device to connect to an AP. As the device moves though out the facility, it may need to associate with a different AP.

AP Signal Strength is a factor here because it has a direct correlation with association time. The Stronger the signal, the faster the association time with a different AP.

To stay on top of this you can use network management tools such as the management console and SNMP to track association metrics.

Site Survey

The process of planning and designing a wireless network, to provide a wireless solution that will deliver the required wireless coverage, data rates, network capacity, roaming capability and quality of service (QoS).

This is extremely important to do; By doing this you can do the following:

Determine if any APs already have range within your facility.

Identify what type of wireless signals you can see in the building.

Allows you to see what frequencies are currently in use and plan the layout according to the interference currently present.

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