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Cisco CCNP ENCOR > Wireless > Flashcards

Wireless Flashcards

1
Q

When looking at a radio wave - what is the relationship of frequency to distance?

A

The higher the frequency of the radio wave, the shorter the distance it will be able to travel.

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2
Q

What is the frequency of a radio wave?

A

The number of oscillations or pulses in a given time period - expressed in Hertz (Hz)

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3
Q

What is the wavelength of a radio wave?

A

The distance between two peaks or valleys of a radio wave.

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4
Q

What is the amplitude of a radio wave?

A

The “height” of a radio wave, which is indicative of it’s power/energy.

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5
Q

In wireless, what are the two purposes to manipulate the amplitude of a wave?

A
  • Increase broadcast distance
  • Convey information or data (using small variations in amplitude)
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6
Q

In wireless, what is the unit of measure for the power of a radio wave’s amplitude?

A

Watts - most wireless signals are expresses in milliwatts, though (1/1,000 of a Watt)

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7
Q

In wireless, what is the function of a Decibel (dB)?

A

To compare two levels of absolute power to each other: the source and the reference

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8
Q

What is EIRP and how is it measured?

A

Effective Isotropic Radiated Power - measured in Decibels (dB), an expression of how powerful a signal is being broadcast:
Transmitter (dB) - Cable Loss (dB) + Antenna Gain (dB)

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9
Q

What is RSSI and how is it measured?

A

Received Signal Strength Indication - expressed as a negative Decimal number relative to 1 milliwatt (-dBm). The lower the negative number, the better the quality of signal. (-20 great, -90 not usable)

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10
Q

What is SNR and how it is measured?

A

Signal to Noise Ratio - in Decibels (dB) its an expression of the difference of our wireless signal over the noise floor. A good number is between 25 - 40 dB.

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11
Q

What are the three most prevalent wireless channels used in the 2.4 Ghz range and why?

A

Channels 1, 6, and 11 - because they are spaced out far enough in the 2.5 Ghz frequency range (2400 Mhz - 2483 Mhz) there is no frequency overlap.

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12
Q

What two characteristics make 802.11ax unique among wireless standards?

A
  • ability to use 1Ghz through 6Ghz frequency
  • Bi-Directional MUMINO (Multi-User Multi-In/Multi-Out)
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13
Q

What is one of the biggest drawbacks of the 802.11ac standard?

A

160Mhz channels has a lot of potential for channel overlap and interference.

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14
Q

When considering any wireless standard that leverages MIMO, what client-side characteristic should be considered?

A

The number of wireless antennas the device has. This will affect multi-path capabilities and throughput.

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15
Q

What wireless standards support some form of MIMO?

A
  • 802.11n
  • 802.11ac
  • 802.11ax
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16
Q

What is the biggest drawback to wireless being a Half-Duplex technology?

A

The slowest client in the “chain” of communication can cause delay for all the others communicating with a given access point.

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17
Q

What is an Isotopic radiation pattern?

A

A theoretically “perfect” radiation pattern where the signal is broadcast evenly in every direction. This is not possible in actuality but used to describe a “perfect scenario” in wireless terms.

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18
Q

What is inefficient about the way a dipole antenna broadcasts a signal?

A

The broadcast signal is weaker above and below the antenna (via the E-Plane)

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19
Q

What is the difference between an Autonomous Access Point and a Light-Weight Access Point?

A

Autonomous: All of the management of the wireless traffic is done on the AP (home router)

Light-Weight: Management and routing decisions are made by Controllers the APs are attached to on the back-end.

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20
Q

What is a WLC?

A

Wireless LAN Controller - a device that manages wireless access-points.

21
Q

What is a BSS and an SSID?

A
  • Basic Service Set
  • Service Set Identifier - The name of the wireless network
22
Q

For an access point operating in Autonomous mode, what is the name of an IP address designated to a given VLAN?

A

BVI - Bridged Virtual Interface

23
Q

What type of layer 2 connection is required to connect to an access point operating in Autonomous mode?

A

Trunk - because multiple VLANs may need to be carried up from the access point.

24
Q

What is the biggest drawback to running APs in autonomous mode?

A

Wireless clients cannot roam between APs because it requires an IP address to change.

25
Q

How does an AP running in Lightweight mode connect back to a Wireless Lan Controller (WLC)?

A

Over a layer 2 CAPWAP tunnel.

26
Q

What are the benefits of using an AP in Lightweight mode

A
  • Lightweight APs can extend VLANs across a WLC
  • Wireless clients can roam between APs without needing an IP address change
  • Management of APs can be centralized to a WLC
  • WLCs can “self-heal” wireless networks
27
Q

What are the drawbacks of using APs in Lightweight mode?

A
  • More complex configuration
  • Clients connecting back to WLCs inside a data center could pose security risks (close virtual proximity to sensitive applications)
  • CAPWAP tunnels connections could bypass a firewall
28
Q

What are the 4 main WLC topology deployment designs?

A
  • Centralized
  • Distributed
  • Branch (Flex Connect)
  • Cloud

NOTE: Fifth option is an SD-Access solution

29
Q

What are the characteristics of a Centralized WLC deployment design?

A
  • There is one (or very few) WLC located in or near the data center
  • WLC controls all lightweight APs
  • Clients connect via CAPWAP tunnel back into a data center subnet
  • Allows for the highest level of Layer 2 roaming for wireless clients
30
Q

What are the characteristics of a Distributed WLC deployment design?

A
  • Multiple WLCs spread across the distribution layer of the network
  • Roaming is limited to APs connected to the same WLC
31
Q

What are the characteristics of a Branch/Flex-Connect WLC deployment design?

A
  • Only Control Plane traffic is sent over the CAPWAP tunnel from the AP
  • Data Plane traffic will be placed on the regular network
  • Guest traffic could still be sent across the CAPWAP tunnel, optionally
  • No Layer 2 roaming for wireless clients
32
Q

What are the characteristics of a Cloud WLC deployment design?

A
  • APs are managed via a Cloud Service (Meraki)
  • the WLC lives in the Cloud
33
Q

What are the two C’s of wireless design?

A
  • Coverage - signal strength and reach
  • Capacity - number of clients that can connect
34
Q

What is the industry standard for wireless coverage overlap of a usable wireless signal between two or more APs?

A

20% traditional overlap
35% coverage overlap for voice and video

35
Q

What is considered the minimum level for a usable wireless signal (dBm)?

A

(-67) to (-70) dBm

NOTE: -67 dBm to support voice and video

36
Q

Which four pieces of Cisco Software can leverage Wireless Real Time Location Service (RTLS)?

A
  • Prime Infrastructure
  • DNA Center
  • DNA Spaces
  • CMX (Connected Mobile eXperiences)
37
Q

What two methods are used by Cisco devices to improve location based service accuracy?

A
  • Triangulation
  • RF Fingerprinting
38
Q

What are the characteristics of a Lightweight Wireless AP configured for “Local” Mode?

A
  • The AP is “local” to the WLC (same subnet or physical location)
  • The default Lightweight mode that offers more BSSs ()
  • The AP will scan other channels, measure noise and interference, detect rogue devices, and match IDS events
39
Q

What are the characteristics of a Lightweight Wireless AP configured for “Bridge” Mode?

A
  • Two APs connect to each other to link to separate locations
  • Multiple APs can be bridged to create a mesh network
40
Q

What are the characteristics of a Lightweight Wireless AP configured for “Flex-Connect” Mode?

A
  • The AP is remote from the WLC
  • The AP can switch traffic locally between an SSID and a VLAN if the CAPWAP tunnel to the WLC is down
41
Q

What are the characteristics of a Lightweight Wireless AP configured for “Rogue detector” Mode?

A
  • the AP is dedicated to detecting rogue devices.

Rogue Devices - a device connected to the wireless and wired networks.

42
Q

What are the characteristics of a Lightweight Wireless AP configured for “Sniffer” Mode?

A
  • The AP only receives traffic for the purpose of sniffing or capturing traffic (i.e. PCAP)
43
Q

What are the characteristics of a Lightweight Wireless AP configured for “Monitor” Mode?

A
  • The AP does not transmit
  • Acts as a sensor for IDS, rogue access points, location-based services
44
Q

What are the characteristics of a Lightweight Wireless AP configured for “SE-Connect” Mode?

A
  • The AP is dedicated to spectrum analysis
  • You can connect to the AP using software like Cisco Spectrum Expert to analyze the data and look for interference.
45
Q

What are the three types of Wireless Ethernet frames?

A
  • Data Frames: Source/Dest MAC headers and CRC
  • Management Frames: Beacon, Probe, Auth, and Association
  • Control Frames: Request to Send (RTS), Clear to Send (CTS), ACK
46
Q

What types of information may be contained in a Beacon Frame?

A
  • SSID
  • Channel
  • Rules: data rates, encryption, power saving
47
Q

What type of request is sent by a client that is actively scanning?

A

Probe Request - searching for an AP that is hosting a known SSID

48
Q

What are the four basic phases a client goes through when trying to join an SSID?

A

1.) Authentication Request (client to AP)
2.) Authentication Response (AP to client) - negotiation of authentication method
3.) Association Request (client to AP)
4.) Association Response (AP to client)

Cisco CCNP ENCOR (22 decks)

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