V1.0 Flashcards

The power source for a dual-band 802.11ac AP must be PoE. What power level should a class 4 device receive from the AP?

Answer: 25.5 W

A Class 4 device, as defined by the IEEE 802.3at (PoE+) standard, requires a minimum of 25.5 Watts of power at the Powered Device (PD). This standard allows for higher power delivery than the original 802.3af (PoE) standard, which provides 12.95W for Class 3 devices.

To implement a WLAN, wireless controllers are used. When turned on and connected to the network, the APs must find the controllers. Which of the following techniques is typically employed by the APs to locate the controllers?

Answer: DHCP

DHCP (Dynamic Host Configuration Protocol) is a common method used by Access Points (APs) to discover wireless controllers. When an AP boots up and receives an IP address via DHCP, the DHCP server can also provide additional configuration options, such as the IP address of the wireless controller, allowing the AP to locate and register with it.

A multi-AP WLAN you create needs fast, secure roaming to function. Which of the following techniques for fast roaming is an IEEE 802.11 standard technique?

Answer: FT

FT stands for Fast Transition, also known as 802.11r. This is an IEEE 802.11 standard designed to enable faster and more secure roaming between Access Points (APs) by allowing clients to pre-authenticate with target APs, significantly reducing the re-association time during a handover.

What 22 MHz channels in an 802.11 2.4 GHz system are regarded as non-overlapping?

Answer: 2 and 8

In the 2.4 GHz band, 802.11 channels are 22 MHz wide and overlap. To minimize interference, non-overlapping channels are chosen such that their frequency ranges do not intersect. Channels 2 (center 2.417 GHz, range approx. 2.406-2.428 GHz) and 8 (center 2.447 GHz, range approx. 2.436-2.458 GHz) are sufficiently separated to be considered non-overlapping, as there is a clear frequency gap between them.

The 2.4 GHz band channel 1's center frequency is 2.412 GHz (2412 MHz). What is channel 4's centred frequency?

Answer: 2.427

In the 2.4 GHz band, each 802.11 channel is separated by 5 MHz. Given that Channel 1's center frequency is 2.412 GHz, Channel 4 is three channels higher (4 - 1 = 3). Therefore, you add 3 * 5 MHz to Channel 1's frequency: 2.412 GHz + (3 * 0.005 GHz) = 2.412 GHz + 0.015 GHz = 2.427 GHz.

According to the specifications for the WLAN you are installing, it must enable unidirectional delays of no more than 150 ms and have a maximum signal intensity of -67 dBm at all receivers. Which application meets these requirements?

Answer: VoIP

VoIP (Voice over IP) applications are highly sensitive to latency and signal quality, requiring low unidirectional delays and strong signal intensity for clear communication. A maximum unidirectional delay of 150 ms and a minimum signal intensity of -67 dBm are typical requirements for reliable VoIP performance, ensuring clear and uninterrupted voice communication. Other applications like E-Mail or FTP are less sensitive to real-time latency.

The access points in your WLAN deployment are set to emit power levels of 10 mW on 2.4 GHz radios and 20 mW on 5 GHz radios. There are also a few semi-directional antennas in use. What sort of deployment is being discussed?

Answer: SOHO

A SOHO (Small Office/Home Office) deployment typically involves a limited number of users and devices, often using lower power levels and a mix of omnidirectional and possibly some semi-directional antennas to cover a smaller area efficiently. The specified power levels (10 mW on 2.4 GHz, 20 mW on 5 GHz) are relatively low, and the mention of 'a few semi-directional antennas' suggests a tailored, smaller-scale setup rather than a large standard office or high-density environment.