Explaining Wireless Fundamentals Flashcards
What is a WPAN? What distance is typically covered?
Wireless Personal Area Network - typically < 5 - 10 meters.
Uses technology like Bluetooth to connect devices.
What is a WLAN, what is the IEEE standard and what is the typical distance covered?
Wireless Local Area Network
IEEE standard = 802.11
< 100 meters (328 feet)
What is a WMAN and what is the typical distance covered?
Wireless Metropolitan Area Network
Commonly provides point-to-point or point-to-multipoint backbone.
Cover distances greater than 100 meters (328 feet or more)
What is an Ad Hoc network?
Connection between two wireless devices.
Creates an Independent Basic Service Set (IBSS).
Contains a limited number of devices because of collision and organization issues.
Also called a peer-to-peer (wireless) network.
What is Wi-Fi Direct and what is the main difference compared to Ad Hoc?
It is an example of a WPAN where connectivity is directly between devices, but is an extension of the infrastructure mode of operation instead of IBSS mode like Ad Hoc networks.
An example of Wi-Fi Direct is Wi-Fi Protected Setup (WPS).
What are the predefined services that Wi-Fi direct brings?
Miracast connections - allow a device to display photos, files and videos on an external monitor or television.
Wi-Fi Direct for Digital Living Network Alliance (DLNA) - lets devices stream music and video between each other.
Wi-Fi Direct Print - ability to print directly from a smart phone, tablet or PC.
What are characteristics of an AP functioning in infrastructure mode?
- AP is a translation bridge between 802.3 (wired media) and 802.11 (wireless media).
- Wireless is a half-duplex environment.
- A basic service area (BSA) is also called a wireless cell.
- A basic service set (BSS) is the service that the AP provides.
What is an ESS?
Extended Service Set
When you put more than one AP in an area, where they work together with shared SSIDs, etc.
What does SSID & BSSID stand for?
Service Set Identifier
Human readable, not unique name of the network.
Basic Service Set Identifier
Unique name of the wireless network, often includes the MAC of the AP. We don’t see this, only the devices do in the
background.
What is the distribution system (or distribution network) within WLAN architectures?
The distribution system (or network) is essentially the wired network or devices that the APs forward their traffic to for distribution.
What are MBSSIDs?
Multiple Basic Service Set Identifiers
It’s like several virtual APs all on the one physical AP so that you can have multiple SSIDs sent out, yet still differentiate the traffic.
What is CAPWAP?
_C_ontrol _a_nd _P_rovisioning of _W_ireless _A_ccess _P_oints
- Uses the Split MAC model.
- Protocol to manage a collection of APs
- includes WLC discovery and join process, AP configuration and firmware push, statistics and security enforcement
- CAPWAP encrypted tunnel formed between WLC and AP
- APs join WLC, then download any new software and configuration changes
- Firewalls should allow UDP 5246 (Control Plane) & UDP 5247 (Data Plane)
What types of vlans are needed for WLANs?
- Management VLAN - for WLC management interface
- AP VLAN - can be the same or different than the management VLAN
- Data VLAN - need VLAN(s) for each SSID on the WLC
What is the switch port configuration for a Centralized AP vs. Standalone AP?
Centralized AP - The switchport is configured as an access port with the ‘AP VLAN’.
Standalone AP - The switchport is configured as a trunk port with allowed VLANs. You also need to configure a native vlan on
the trunk for the AP to properly be managed. [Example - Switch1 (config-if)#switchport trunk native vlan 12]
What is a WGB?
Workgroup Bridge
An AP that provides a wired device connected to it’s ethernet port a wireless connection back to the rest of the network. WGBs can also connect to switches to provide multiple wired devices with connectivity.
What is a wireless Mesh Network?
Connecting one AP to another AP wirelessly to provide connectivity to devices where you cannot run a wire to connect the AP to the network.
The mesh APs use one radio (typically 2.4GHz) for clients and their other radio (typically 5GHz) for backhaul traffic to other APs.
What are the different operational frequencies and data rates for IEEE 802.11 standards & amendments?
- 11 - 2.4 GHz / 1, 2 Mbps
- 11a - 5 GHz / 6, 9, 12, 18, 24, 36, 48, 54 Mbps
- 11b - 2.4 GHz / 1, 2, 5.5, 11, 6, 9, 12, 18, 24, 36, 48, 54 Mbps
- 11n - 2.4 GHz and 5 GHz / Up to 600 Mbps
- 11ac - 5 GHz / Up to 3500 Mbps
What are the ISM band ranges for 2.4 GHz wireless?
- 4 to 2.4835 (in Japan 2.497)
- ISM stands for industrial, scientific, and medical.
- 22 MHz wide channels, resulting in 11 channels (US), 13 channels (Europe) or 14 channels (Japan)
- Each channel is separated by 5 MHz so there 3 non-overlapping channels in the US and Europe, 4 in Japan.
- 802.11n allows for 40 MHz wide channels, but only feasible in residential because you reduce the non-overlapping channels.
What are the 5 GHz UNII and ISM bands?
-UNII stands for Unlicensed National Information Infrastructure
UNII-1 - ranges from 5.15 to 5.25 GHz
UNII-2 - ranges from 5.25 to 5.35 GHz
UNII-2 extended - ranges from 5.470 to 5.725 GHz
UNII-3 - ranges from 5.725 to 5.825 GHz
ISM ranges from 5.725 to 5.875 GHz (overlaps with UNII-3 band)
What is the difference in co-channel interference and adjacent channel interference?
Co-Channel Interference - APs share the same channel and cause slow connectivity.
Adjacent Channel Interference - APs use different overlapping channels, causes collisions which disrupts wireless operation.
What is the difference in 2.4 GHz and 5 GHz wireless?
2.4 GHz has greater range and propagation through obstacles. However many more potential interferences and less channels to avoid overlaps.
5 GHz has less range, older devices are sometimes not supported and can still have interference from things like weather radars.
What is the DHCP options needed for IPv4 and IPv6 for APs to map to their WLC?
IPv4 - DHCP Option 43
IPv6 - DHCP Option 52
What are the 2 ways to implement DHCP with WLANs?
- Using an internal DHCP server on the Cisco WLC
- typically done at a branch office that does not have a DHCP server
- however, DHCP Option 43 (or 52) is not supported, so the APs must have another way to find the WLC such as a local
subnet broadcast or DNS
- Using a switch or router as a DHCP server.
- preferred method when possible
What are the steps of the DNS discovery option mode for APs?
- AP requests its IPv4 address from DHCP, and includes Options 6 (DNS server address) and Option 15 (Domain name)
- The IPv4 address of the DNS server is provided by the DHCP server from the DHCP option 6
- The AP will do a hostname lookup using CISCO-CAPWAP-CONTROLLER.localdomain. This hostname should be associated to the available Cisco WLC management interface IP addresses (IPv4, IPv6, or both)
- The AP will then be able to associate to responsive WLCs by sending packets to the provided address.
