12.8.2 Module Quiz – WLAN Concepts (Answers)

Explanation: Tethering allows a laptop or PC to use the Internet connection of a mobile device such as a cell phone, usually through a cellular data connection. This allows devices to connect to the Internet in locations where there is no Wi-Fi or cabled connection, but where there is still a cellular data connection.

Explanation: Multiple-input multiple-output (MIMO) technology allows 802.11n devices to use multiple antennas in order to increase the available bandwidth for the wireless network. Single Point Setup (SPS) is a Cisco technology that makes AP deployment easier by supporting clustering from a single management interface. Wi-Fi Protected Setup (WPS) is used to simplify connecting clients to secure wireless networks. Man-in-the-middle (MITM) is a type of security attack where the attacker attempts to insert themselves into the middle of a data stream.

Explanation: WPA2 can use the AES encryption standard, which is currently the strongest method of encrypting wireless data.

Explanation: The SSID is used to name a wireless network. This parameter is required in order for a wireless client to attach to a wireless AP.

Explanation: A wireless client operating in active mode must know the name of the SSID. Probe requests are broadcast by a client across multiple channels and include the SSID name and supported standards. Active mode is used if an AP is configured to not broadcast beacon frames.

Explanation: The 802.11n standard is backwards compatible with both the 802.11a and 802.11b standards and therefore operates at both 5 GHz and 2.4 GHz.

Explanation: An autonomous access point is used in environments that require a small number of access points. As network demands increase, more access points can be added to the environment with each access point acting independently of another. An autonomous access point can be configured using either a GUI or CLI.

Explanation: In addition to its roles as router, a typical SOHO wireless router acts as both a wireless access point and an Ethernet switch. RADIUS authentication is provided by an external server. A WLAN controller is used in enterprise deployments to manage groups of lightweight access points. A repeater is a device that enhances an incoming signal and retransmits it.

Explanation: CAPWAP can operate either over IPv4 or IPv6 and can use UDP ports 5246 and 5247.

Explanation: In order to minimize interference, one of the three non-overlapping channels should be used in 2.4GHz Wi-Fi networks: 1, 6, or 11.

Explanation: Internet access by means of satellites is available across the world. Temporary installations, airplanes in flight, and naval vessels benefit from the use of satellite internet. Municipal Wi-Fi, WiMax, and cellular technology are not able to support the mobile requirements of naval vessels and airplanes in transit.

Explanation: Tethering enables a wireless device such as a phone to provide wireless Internet connectivity to other devices, thus creating a hotspot. Infrastructure mode is the type of wireless network that is created when an access point is being used. Mixed mode allows older wireless NICs to attach to an access point that can use a newer wireless standard.

Explanation: Wireless devices operate in either ad hoc or infrastructure modes. An ad hoc WLAN, also referred to as an independent basic service set (IBISS), operates on a peer-to-peer basis without a network. Infrastructure modes can consist of a single Basic Service Set (BSS) with an AP interconnecting associated stations, or an Extended Service Set (ESS), with two or more BSSes interconnected over a wire distribution system such as Ethernet. WiFi Direct is a compatibility certification unrelated to WLAN topologies.

Explanation: Beacon frames are broadcast periodically by the AP to advertise its wireless networks to potential clients. Probing, association, and authentication frames are only sent when a client is associating to the AP.

Explanation: Beacons are the only management frame that may regularly be broadcast by an AP. Probing, authentication, and association frames are used only during the association (or reassociation) process.

Explanation: Omnidirectional antennas send the radio signals in a 360 degree pattern around the antenna. This provides coverage to devices situated anywhere around the access point. Dishes, directional, and Yagi antennas focus the radio signals in a single direction, making them less suitable for covering large, open areas.

Explanation: SSID cloaking is a weak security feature that is performed by APs and some wireless routers by allowing the SSID beacon frame to be disabled. Although clients have to manually identify the SSID to be connected to the network, the SSID can be easily discovered.

Explanation: Two methods can be used by a wireless device to discover and register with an access point: passive mode and active mode. In passive mode, the AP sends a broadcast beacon frame that contains the SSID and other wireless settings. In active mode, the wireless device must be manually configured for the SSID, and then the device broadcasts a probe request.

Explanation: Ad hoc mode (also known as independent basic service set or IBSS) is used in a peer-to-peer wireless network, such as when Bluetooth is used. A variation of the ad hoc topology exists when a smart phone or tablet with cellular data access is enabled to create a personal wireless hotspot. Mixed mode allows older wireless NICs to attach to an access point that can use a newer wireless standard.

Explanation: The 802.11a and 802.11ac standards operate only in the 5 GHZ range. The 802.11b and 802.11g standards operate only in the 2.4 GHz range. The 802.11n standard operates in both the 2.4 and 5 GHz ranges. The 802.11ad standard operates in the 2.4, 5, and 60 GHz ranges.

Explanation: 802.11ac provides data rates up to 1.3 Gbps and is still backward compatible with 802.11a/b/g/n devices. 802.11g and 802.11n are older standards that cannot reach speeds over 1 Gbps.

Explanation: Interference occurs when one signal overlaps a channel reserved for another signal, causing possible distortion. The best practice for 2.4 GHz WLANs that require multiple APs is to use the non-overlapping channels 1, 6, and 11. These are selected because they are 5 channels apart and therefore minimize the interference with adjacent channels.

Explanation: WPA and WPA2 Personal are intended for home or small office networks where users authenticate using a pre-shared key (PSK). WPA and WPA2 Enterprise is intended for enterprise networks but requires a RADIUS authentication server which provides additional security. WEP Enterprise is not a valid option.

Explanation: When an access point is configured in passive mode, the SSID is broadcast so that the name of wireless network will appear in the listing of available networks for clients. Active is a mode used to configure an access point so that clients must know the SSID to connect to the access point. APs and wireless routers can operate in a mixed mode, meaning that that multiple wireless standards are supported. Open is an authentication mode for an access point that has no impact on the listing of available wireless networks for a client.