Troubleshooting Wireless Networks Flashcards
Bandwidth
Theoretical speed of data going across the network
Throughput
Actual speed of data on the network
RSSI
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?
EIRP
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
dBi
Decibels over Isotropic:
Tells signal strength being radiated from a WAP
Vertical Antenna
Radio frequency waves extend outward in all directions away from the
antenna and the wireless access point at an equal power level
Dipole Antenna
Produces radio frequency waves extending outward in two directions
Yagi Antenna
A unidirectional antenna that sends the radio frequency waves in only
one direction
Parabolic Grid Antenna
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
Polarization
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)
Channel Utilization
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
CCA
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
Site Survey
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
Wireless 802.11 Notes
- 11n: Doubled the distance over earlier (a/b/g) networks.
- 11ac/802.11ax: Cover a distance between n and earlier (a/b/g), but have much higher speeds/throughputs
Site Survey: Basic Steps
Scan airwaves Find APs Request association Authenticate Contact DHCP server
Coverage
A measure of how much area around a wireless transmitter is there
sufficient signal strength for wireless devices to utilize
Interference
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
Attenuation
Reduction of signal strength between the transmission and receipt of the
signal
Multipath Reception
Occurs when the transmitted signal bounces off walls and other physical
objects and then is redirected to the receiver
Client Disassociation: Idle Timeout
Occurs when there’s no traffic within 300 seconds
Send a keep alive packet every few minutes to
remain connected
Client Disassociation: Session Timeout
Occurs when there’s no traffic within 1800 seconds
Client Disassociation: Access Point Radio Reset
Occurs when a change is made to the wireless network
Encryption Mismatch
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
HTTP Redirect
Redirects all traffic to a web server which then redirects them to a captive portal using a 302 HTTP status code
ICMP Redirect
Sends error messages and operational information indicating the success or failure of communicating with another IP address
DNS Redirect
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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