Troubleshooting Wireless Networks

Question 1

Bandwidth

Answer 1

Theoretical speed of data going across the network

Question 2

Throughput

Answer 2

Actual speed of data on the network

Question 3

RSSI

Answer 3

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

Ideal: -60 to -65 dB range = Strong Signal

Is the client having issues receiving the signal?

Question 4

EIRP

Answer 4

Effective Equivalent Isotropic Radiated Power:
Maximum power radiated from an ideal isotropic antenna, given its antenna gain, & the transmitter power of the radio frequency system

Is the access point having issues?

RSSI = Client Level
EIRP = AP Level

Question 5

dBi

Answer 5

Decibels over Isotropic:

Tells signal strength being radiated from a WAP

Question 6

Vertical Antenna

Answer 6

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

Question 7

Dipole Antenna

Answer 7

Produces radio frequency waves extending outward in two directions

Question 8

Yagi Antenna

Answer 8

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

Question 9

Parabolic Grid Antenna

Answer 9

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

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

For indoor use, you are more likely to use omnidirectional and
unidirectional antennas

Question 10

Polarization

Answer 10

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

Most Wi-Fi networks use vertical polarization

Low RSSI when close to antenna? May be polarization issue (bend antenna)

Question 11

Channel Utilization

Answer 11

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

Keep channel utilization under 30% to have a faster wireless network

Access points and clients form a single broadcast domain when they
operate on the same channel

Question 12

CCA

Answer 12

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

High channel utilization leads to slower throughput for wireless networks

Question 13

Site Survey

Answer 13

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

Configure devices to use less utilized channels
Ensure proper coverage of the entire work areas

Ensure wireless network is not being blocked or interfering with
physical obstacles within the building

Question 14

Wireless 802.11 Notes

Answer 14

802. 11n: Doubled the distance over earlier (a/b/g) networks.
803. 11ac/802.11ax: Cover a distance between n and earlier (a/b/g), but have much higher speeds/throughputs

Question 15

Site Survey: Basic Steps

Answer 15

Scan airwaves
Find APs
Request association
Authenticate
Contact DHCP server

Question 16

Coverage

Answer 16

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

Question 17

Interference

Answer 17

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

Use channels 1, 6, and 11 in the 2.4 GHz spectrum

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

Question 18

Attenuation

Answer 18

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

Question 19

Multipath Reception

Answer 19

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

Question 20

Client Disassociation: Idle Timeout

Answer 20

Occurs when there’s no traffic within 300 seconds

Send a keep alive packet every few minutes to
remain connected

Question 21

Client Disassociation: Session Timeout

Answer 21

Occurs when there’s no traffic within 1800 seconds

Question 22

Client Disassociation: Access Point Radio Reset

Answer 22

Occurs when a change is made to the wireless network

Question 23

Encryption Mismatch

Answer 23

Occurs when the client and the access point are using different
encryption types

To fix this, attempt to reinstall the drivers for your wireless adapter
Change protocol type
Disable antivirus tools
Reinstall drivers

Question 24

HTTP Redirect

Answer 24

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

Question 25

ICMP Redirect

Answer 25

Sends error messages and operational information indicating the success or failure of communicating with another IP address

Question 26

DNS Redirect

Answer 26

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

If that doesn’t work, determine your default gateway for the
wireless network and enter http:// and the default gateway’s IP
address, then press enter

If that doesn’t work, then verify your DNS server IPs are not set to
something manually like 8.8.8.8, and instead allow DHCP to
autoconfigure your DNS server when connecting to the wireless
network

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