Troubleshooting Wireless Issues

Question 1

The theoretical speed of data going across the network

Answer 1

Bandwidth

Question 2

The actual speed of data on the network

Answer 2

Throughput

Question 3

802.11a - 54 Mbps/bandwidth - 20-30 Mbps/Throughput

802.11b - 11 Mbps - 5-7 Mbps

802.11g - 54 Mbps - 30-32 Mbps

802.11n - 600 Mbps - 140-150 Mbps

802.11ac - 1300 Mbps/1900 Mbps - 100-500 Mbps

802.11ax - 10 Gbps - 600-900 Mbps

Answer 3

802.11n has doubled the distance over A,B and G networks

Aware that wireless AC & AX will cover a distance between wireless N and the other earlier technologies of A,B, C and G

Question 4

Estimated measure of the power level that a radio frequency client device is receiving from a wireless access point or wireless router

Answer 4

Received Signal Strength indicator (RSSI)

Question 5

When you’re looking at RSSI:

Answer 5

Over -90 db - Extremely week

Around -65 dB - Fairly strong

-55 db - Strong signal

-30 or above - Extremely strong

Question 6

The maximum amount of power that could be radiated from an ideal isotropic antenna, given its antenna gain, and the transmitter power of the radio frequency system

Answer 6

Effective Isotropic Radiated Power (EIRP)

Question 7

Usually measured in Decibels over isotropic (dBi)

Answer 7

RSSI - Signal received

EIRP - Signal sent

Question 8

A measure of how much area around a wireless transmitter there is sufficient signal strength for wireless devices to utilize

Answer 8

Coverage

Question 9

Client - RSSI (decibel)

Access Point - EIRP (dBI)

Question 10

One of the most common issues experienced by wifi users is:

Answer 10

Insufficient wireless coverage

Question 11

RSSI decreases whenever the signal has to penetrate through the floor

Question 12

Find a way to boost up that signal and make it stronger so you can increase your coverage area:

Answer 12

Signal booster

Larger antenna

Wireless repeater - A layer one device that has two radios built into it

Second access point

Question 13

Remember, the coverage area for a signal wireless access point

Answer 13

The amount of power transmitted

The size of the antenna

Question 14

A combination of repeaters and access points integrated into a single device to offer complete coverage for larger homes and offices

Answer 14

Wireless Mesh System

Question 15

Occurs when multiple wireless networks communicate on the same channel using the same frequency

Answer 15

Interference

Question 16

Remember, in a 2.4 gigahertz network, you always want to make sure you’re using channels

Answer 16

1, 6, and 11 in the 2.4 GHz spectrum

Question 17

You never want two of the same channel number sitting next to each other and overlapping

Answer 17

Ensure a 10-15% overlap between access points for sufficient coverage

Question 18

Reduction of signal strength between the transmission and receipt of the signal

Answer 18

Attenuation

Question 19

To improve signal strength and reduce attenuation, use higher quality, lower-resistant cables or antennas

Question 20

Occurs when the transmitted signal bounces off walls and other physical objects and then get redirected to the receiver

Answer 20

Multipath Reception

Question 21

This can result in a lower RSSI value and reduced throughput for data transmitted over then networks

Question 22

What are some reasons that a client would be disassociated from a wireless access points

Answer 22

Idle timeout - Occurs when there’s no traffic within 300 seconds | send a keep alive packet every few minutes to remain connected

Session timeout - Occurs when there’s no traffic within 1800 seconds

Wireless network change - Occurs whenever the wireless local area network is changed

Manual deletion - Occurs whenever a client is removed by an administrator

Authentication timeout - Occurs when the authentication or key exchange process fails to finish in time

Access point radio reset - Occurs when a change is made to the wireless network

Question 23

A common wireless attack used by hackers to disassociate wireless clients and make them attempt to reconnect to the access point

Answer 23

Deauthentication Attack

Question 24

If you see a client that’s continually being de-authenticated,

Answer 24

Check wireless gateways & wireless controller logs to determine the root cause

If cause by an attacker, investagiate further

Question 25

What are the few incorrect configurations issues within wireless networks

Answer 25

Wrong SSID - A natural language name used to identify a wireless networks in an 802.11 network | it's crucial to avoid mistyping to prevent an incorrect SSID error Incorrect passphrase - attempt to reinstall the drivers for the wireless adapter Encryption mismatch - wrong password or wrong encryption protocol Try: 1. Change protocol type 2. Disable antivirus tools 3. Reinstall wireless drivers for your wireless network adapter

Question 26

WEP - RC4 WPA - TKIP WPA2 - AES

Question 27

A web page displayed to newly-connected wifi users before being granted broader access to network resources

Answer 27

Captive Portal

Question 28

Redirects all traffic to a web server which then redirects them to a captive portal using a 302 HTTP status code

Answer 28

HTTP Redirect

Question 29

Sends error message and operational info indicating the success or failure of communicating with another IP address

Answer 29

ICMP Redirect

Question 30

The client is redirected by the onboard DNS server to the captive portal webpage

Answer 30

DNS Redirect

Question 31

3 step troubleshooting process:

Answer 31

1. Open a web browser and try to go to any website 2. Determine default gateway for wireless network and enter http:// and default gateway's IP address, then press enter 3. Verify DNS server IPs and allow DHCP to auto-configure the DNS server when connecting to the wireless network

Question 32

By default, most wireless access points use omnidirectional antennas

Question 33

Radio frequency waves extend outward in all directions away from the antenna and the wireless access point at an equal power level

Answer 33

Vertical Antenna

Question 34

Produces radio frequency waves extending outward in two directions

Answer 34

Dipole Antenna

Question 35

A unidirectional antenna that sends the radio frequency waves is only one direction

Answer 35

Yagi Antenna

Question 36

Allows the radio waves to be transmitted in only one direction over a longer distance than a Yagi antenna

Answer 36

Parabolic Grind Antenna

Question 37

Choose a parabolic or Yagi antenna for site-to-site connections

Answer 37

For indoor applications, omnidirectional and unidirectional antennas are more commonly used

Question 38

Omnidirectional - On the ceiling Unidirectional - On the outer wall

Question 39

The orientation of the electric field (or transmission) from the antenna

Answer 39

Polarization

Question 40

For wifi networks our antennas usually are going to have a vertical or horizontal polarization associated with them

Answer 40

Most wi-fi networks use vertical polarization

Question 41

A statistic or measure of the amount of airtime utilization that occurs for particular frequency or channel

Answer 41

Channel Utilization

Question 42

In order to have a fast wireless network:

Answer 42

You want to keep your channel utilization under around 30%

Question 43

Access points and clients create a single broadcast domain when operating on the same channel

Answer 43

To prevent collisions, 802.11 wireless devices employ a "listen before they speak" approach when accessing the wireless medium

Question 44

Listens to see if another device is actively transmitting on the channel before attempting to send frames on that channel

Answer 44

Clear Channel Assessment (CCA)

Question 45

High channel utilization leads to slower throughput for wireless networks

Question 46

Process of planning and designing a wireless network to provide the required wireless solution

Answer 46

Site Survey

Question 47

Utilizing the 5 GHz spectrum provides 24 non-overlapping channels

Question 48

By conducting a site survey, you can better understand the wireless environment in and around your network

Answer 48

Configure devices to use less utilized channels Ensure proper coverage of the entire work areas Ensure wireless network is not being blocked or interfered with by physical obstacles within the building

Question 49

Wireless access point association times - When a wireless client attempts to connect to a wireless network, it goes through a seven step process.

Answer 49

1. Wireless client sends a probe request to discover any 802.11 wireless networks in proximity to itself 2. Receiving access point checks to see if it can support the data rate the client requested 3. Wireless client sends a low-level 802.11 authentication frame to the access point to begin authentication 4. Access point receives an authentication frame and responds with an acknowledgment to proceed with the handshake 5. Wireless client chooses the access point it wants to associate with and sends an association request 6. Access point processes the association request if the information sent matches its capabilities 7. Client is fully connected and associated and can now conduct any data transfer it needs and use the wireless network

Question 50

Sometimes you're going to see a wireless network that has a really long association time for an user's client

Answer 50

Scan airwaves, Find access points, request association, authenticate, contact DHCP server

Question 51

Clients should be located in high signal strength areas to speed up the association process

Question 52

Donna, a customer experience manager on the upper floors of a large corporate building, has frequently experienced dropped connections and slow internet speeds. The IT department conducts tests and finds that the Wi-Fi signal strength diminishes significantly as you move higher in the building. What is the most likely issue?

Answer 52

Insufficient wireless coverage

Question 53

Albert works as a production assistant in a large corporate environment that relies on a wireless network for their day-to-day tasks. Recently, some of his co-workers have reported sudden disconnections from the Wi-Fi network, especially when moving between different areas of the office. Despite having a strong Wi-Fi signal, these disconnections occur randomly and affect multiple devices. Additionally, there have been no recent changes to the network configuration or equipment. What is the most likely issue causing the sudden disconnections experienced by employees?

Answer 53

Client disassociation issues - Sudden disconnections when moving suggest client issues

Question 54

In a suburban neighborhood, residents subscribe to the same internet service provider (ISP) and utilize Wi-Fi for their home networks. Recently, several households have been experiencing intermittent connectivity issues and fluctuations in internet speed. Despite having high-speed internet packages, some residents notice that their Wi-Fi signal strength weakens significantly during certain times of the day, particularly in the evening when many households are online simultaneously. Additionally, the distance between the Wi-Fi routers and the devices within these households remains relatively consistent. What is the most likely cause of the connectivity issues and fluctuations in internet speed experienced by residents?

Answer 54

Signal degradation - Intermittent connectivity during during peak hours suggests signal weakening/degrading, likely due to overcrowded channels or environmental factors

Question 55

Denise manages a small design studio where employees frequently move around the open workspace to collaborate on various projects. However, they encounter frequent disruptions to their internet connection when transitioning between different zones. Despite the studio's compact layout, the Wi-Fi network fails to seamlessly hand off connections between access points (APs), leading to frustration and delays in completing tasks. Despite attempts to troubleshoot the issue, such as relocating routers and adjusting settings, the problem persists, hindering productivity. What is the likely cause of the frequent disruptions to the internet connection for employees in the design studio?

Answer 55

Roaming misconfiguration between access points - Frequent disruptions during transitions between zones, points towards a roaming misconfiguration, where devices fail to smoothly switch between APs

Question 56

In a wireless network deployment, users in certain areas experience intermittent connectivity issues despite having strong signal strength. Upon investigation, it's discovered that neighboring access points (APs) are operating on frequencies that interfere with each other, resulting in disrupted communication for connected devices. What is the likely primary cause of the connectivity issues?

Answer 56

Channel overlap - In this scenario, neighboring access points operating on conflicting frequencies cause interference, leading to disrupted communication.