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CCNP Core > Chap 21 - Troubleshooting Wireless Connectivity > Flashcards

Chap 21 - Troubleshooting Wireless Connectivity Flashcards

1
Q

What is the first thing you should do when troubleshooting wireless connectivity?

A

Get more information.

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2
Q

What 3 conditions must be met in order for a client to connect to the wireless network?

A
  • Client within range of an AP and asks to connect
  • Client authenticates
  • Client requests and receives an IP address *
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3
Q

What do you need at a minimum to begin troubleshooting a client’s connectivity issue?

A
  • MAC address of the clients wireless NIC
  • Client’s physical location
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4
Q

How is the access point chosen for the client to connect to?

A

The client’s machine chooses it.

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5
Q

What are the 5 steps a client progresses through when connecting?

A
  • Start
  • Association (client requested 802.11 auth)
  • Authentication (layer 2 PSK or 802.1x)
  • DHCP (getting IP address)
  • Online (layer 2 and 3 policies passed, successfully associated)
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6
Q

How can you tell which states the client has passed?

A

The dots in the Connectivity box are green if passed, black if not.

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7
Q

What 13 pieces of information about the client is displayed on the left side of the Client View screen?

A
  • Client’s username
  • Host name
  • MAC address
  • Wireless connection up time
  • SSID
  • AP name
  • Nearest neighbor APs along with signal strengths
  • Client’s Device Type
  • Performance
  • Clients Capabilities
  • Cisco Compatible
  • Connection Score
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8
Q

What are 3 ranges of Poor, Good, and Excellent SNR measurements?

A
  • Poor - 16-24 dB
  • Good - 25-40 dB
  • Excellent - 41 dB or higher
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9
Q

What are 3 dBm measurements of Signal Strength from poor to excellent?

A
  • -70 dBm is poor (light browsing and email)
    • 60 dBm is good
  • -50 dBm is excellent
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10
Q

How is the connection score calculated?

A

Client’s current data rate divided by the lower maximum supported rate of either the client or the AP.

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11
Q

In the Performance Section of the Client view what 4 things does it show?

A
  • Signal strength
  • Signal quality
  • Connection speed
  • Channel width
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12
Q

Where is the Connection Score shown?

A

Client View left side below Cisco Compatible

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13
Q

If you click on Connection Score what 6 items will be displayed?

A
  • Connection score
  • AP max data rate
  • Client max data rate
  • Client actual data rate
  • Spatial streams
  • Channel width
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14
Q

Where is the Mobility State?

A

Client Search info below the General and Connectivity sections -> Client Mobility State

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15
Q

What 7 things does the Mobility State show?

A
  • The WLC the client is on
  • WLC name, IP, and model info
  • AP name, IP, model
  • Type of connection (wired over CAPWAP)
  • Which band (2.4 or 5 GHz)
  • Which 802.x protocol
  • Client device name, type, VLAN, and IP
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16
Q

What 5 items are shown in the Client’s Wireless Policies?

A
  • Client’s IP, VLAN
  • QOS policy
  • Security policy (WPA2)
  • Encryption cypher
  • Authentication type
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17
Q

What are the 4 client test tools?

A
  • Ping test
  • Connection debug
  • Event log
  • Packet capture
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18
Q

What does the Ping test consist of?

A

5 ICMP echo packets and measures response time

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19
Q

What does the Connection test consist of?

A
  • 3 minute debug
  • Checks each policy step
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20
Q

What does the Event log show?

A

Collects and displays a log of events as the client attempts to join the network

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21
Q

What does the Packet Capture tool do, where is the capture stored, and how can it be viewed?

A
  • Captures packets at the AP
  • Saved to FTP server
  • Can be viewed with Wireshark or Omnipeek
22
Q

What 2 connections are required for the AP to work?

A
  • Connectivity to its access layer switch
  • Connectivity to the WLC (unless operating in FlexConnect mode)
23
Q

On the WLC in the Access Point View what is shown on the left?

A
  • AP name
  • IP address
  • CDP info (connected switch and port)
  • Model
  • Power status
  • Serial number
  • Capabilities
24
Q

On the WLC in the Access Point View what 11 things are shown on the right?

A
  • Wireless performance
  • RF conditions
  • Number of clients
  • Number of radios
  • Channels being used
  • Amount of traffic
  • Avg throughput
  • Transmit power
  • Channel utilization (use of the channel by ANY AP that this AP can hear)
  • Noise level on each channel
  • Clean Air status (air quality)
25
Q

Which band has channels that are usually more noisy - 2.4 GHz or 5 GHz?

A

2.4 GHz channels are usually more noisy.

26
Q

What is acceptable noise level?

A

Noise level should be -90 or -100 dBm (the lower the better - -80 is too high)

27
Q

What is Air Quality?

A

A measure of how competing and interfering devices affect the airtime quality or performance on a channel, presented as a number from 0 (worst) to 100 (best).

28
Q

How does an AP calculate Air Quality?

A

Every Cisco AP has a built-in Spectrum Analyzer.

29
Q

Where can you get more info on a Clean Air Interferer?

A
  • RF Troubleshoot Tab
  • Click on Clean Air tab
30
Q

What does the Severity indicator show?

A

It is an indication of how badly the interferer is affecting the channel.

31
Q

What does Duty Cycle mean?

A

It shows how often the interference occurs (100% would be all the time)

32
Q

Where can you view which of the 5 states a client has passed?

A

Client View -> Connectivity box

33
Q

Where is the Performance section?

A

Client View

34
Q

Where are the 4 Client Test Tools located?

A

Client search information -> at the bottom

35
Q

What dBm measurement of RSSI is considered reliable?

A

-67 dBm

36
Q

Where are the Client’s wireless policies located?

A

Client search info below Mobility State

37
Q

On the left side of the Client View what information does the Performance field show?

A
  • Signal Strength
  • Signal Quality
  • Connection Speed
  • Channel Width
38
Q

In the Performance Summary section of the Access Point View what is channel utilization an indication of?

A

It’s an indication of how much of the available air time is being used

39
Q

If channel utilization is high what does that mean for a wireless device on that channel?

A

That there is less time available for wireless devices to claim the channel and transmit

40
Q

In Access Point View what might it mean if channel utilization is high but there are no clients attached to the AP?

A

It could mean that there is another AP within range on the same channel. The AP you are looking at would register the other APs use of the channel as channel utilization.

41
Q

In Access Point View -> Details, what are the 4 tabs?

A
  • Clients
  • RF Troubleshoot
  • Clean Air
  • Tools (a tool to reboot the AP)
42
Q

If a client has a static IP address assigned what will the Connectivity box show when it gets to DHCP?

A

If the WLAN is configured to NOT require DHCP the client will move past the DHCP stage.

43
Q

What does it mean if no user name is shown in the Client View?

A

The client didn’t authenticate with a username

44
Q

Client starts with good signal, snr, and connection score, 10 min later he has a bad signal, snr and connection score. What are 2 things this would indicate?

A
  • Client has moved away from the AP so maybe another AP is needed in that area
  • The client device is not roaming soon enough to an AP with a stronger signal
45
Q

Several clients in the same area report no signal from AP. What could that be an indication of and what might you have to do?

A

Could be a defective radio. You might have to go there to confirm there is no signal.

46
Q

What should Noise Level be in order for 802.11 signals can be heard and what is considered high noise level?

A
  • It should be -90 dBm or -100 dBm
  • -80 dBm is considered high
47
Q

What Air Quality measurement would be concerning?

A

59

48
Q

In general what is Noise?

A

Generally considered to be energy received from non-802.11 sources.

49
Q

If an interferer is detected and Clean Air is showing high severity what are 3 options to resolve the issue?

A
  • Disable the interferer
  • Move the interferer to an unused channel
  • Reconfigure the AP to use a different channel.
50
Q

In Access Point View -> Performance Summary -> Air Quality, if a device shows an Air Quality of 59 what 2 steps would you take to determine the source of the poor Air Quality?

A
  • Go to RF Troubleshoot and check Clean Air Interferers
  • Then go to Clean Air tab and check Non-WiFi Channel Utilization
51
Q

What is 802.11W and what does it specify?

A
  • The standard for Protected Management Frames (PMF).
  • It protects against spoofed management frames in a wireless network.

CCNP Core (46 decks)

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