Sunday, July 19, 2015

1.4.2 RF Gain/Loss

RF Gain/Loss

WiFi uses RF to transmit data. The signals amplitude decreases as it travels away from the source. Think of the area of the wave increasing. As the area increases, the amount of signal that hits the receiving antenna is decreased (most of the signal spreads out in other directions). The rate of decrease is affected by the material the wave passes through. Even if the wave hits no obstructions, it will still decrease. This is called Free Space Path Loss. The free space path loss in dB can be calculated according to the following equation:

FSPL (dB) = 20log 10 (d) + 20log 10 (f) + 32.44

As you can see, the loss is proportional to both the distance and the frequency. The higher frequencies (of the 5GHz band) will be attenuated more than lower (2.4GHz) frequencies. This is one reason why 2.4GHz WiFi bands cover a larger area than 5GHz bands.
When an RF signal passes through other materials such as walls, windows and people, the annuation is greater than the FSPL.

Antennas are used to amplify the signal. Remember antennas amplify both the transmitted signal and the received signal. So an antenna on an AP will improve the reception of WiFi signals as well as the transmission.

The link budget is the combination of gains and losses between the transmitter and the receiver. It is the transmit power – cable loss + transmit antenna gain – path loss + receive antenna gain – cable loss.

Sunday, July 12, 2015

1.6.1 IBSS

IBSS - Independent Basic Service Set

Also known as an ad-hoc network, an IBSS is when end devices communicate via WiFi without an AP. One device set up the IBSS – SSID name and other parameters. Other devices can join this IBSS if they have the authentication parameters and communicate directly. An IBSS does not scale well. There is no central control. Services such an IP addressing must be performed manually etc.

1.4.5 Reflection

Reflection The effect of an RF signal meeting a dense, reflective material, such that it is sent in a different direction

If an RF signal traveling as a wave meets a dense reflective material, the signal can be reflected just like a light wave is reflected off of certain surfaces. In a wireless LAN scenario, the wave will reflect off metal surfaces such as filing cabinets etc or off windows. There would also be some level of reflection from walls and in outdoor deployment from the earth, buildings and water.
The reflection is a copy of the signal and if it is received along with the original signal (straight path) then it is likely to be out of phase. This causes the net received signal to be less. This is known as multipath. Prior to 802.11n, multipath was always detrimental. In 802.11n/ac, multipath has been harnessed to improve the performance of the transmission/reception train.

Saturday, July 11, 2015

1.4.4 Refraction

When an RF signal meets the boundary between media of two different densities, it can also be refracted. Think of reflection as bouncing off a surface and refraction as being bent while passing through a surface.

A refracted signal will have a different angle from the original. The speed of the wave can also be affected as it passes through the different materials. A signal can be refracted when it passes through layers of air having different densities or through building walls with different densities, for example.

1.4.3 EIRP

EIRP - effective isotropic radiated power (EIRP) The resulting signal power level, measured in dBm, of the combination of a transmitter, cable, and an antenna, as measured at the antenna
Once you know the complete combination of transmitter power level, the length of cable, and the antenna gain, you can figure out the actual power level that will be radiated from the antenna. This is known as the effective isotropic radiated power (EIRP), measured in dBm.
EIRP is a very important parameter because it is regulated by governmental agencies in most countries. In those cases, a system cannot radiate signals higher than a maximum allowable EIRP. To find the EIRP of a system, simply add the transmitter power level to the antenna gain and subtract the cable loss.
When you work with wireless LAN devices, the EIRP levels leaving the transmitter’s antenna normally range from 100 mW down to 1 mW. This corresponds to the range +20 dBm down to 0 dBm.

Allowed Use
Transmitter Max
2.4Ghz ISM
Indoor or outdoor
30 dBm (1 W)
36 dBm
Indoor only
17 dBm (50 mW)
23 dBm
Indoor or outdoor
24 dBm (250 mW)
30 dBm
Extended Indoor or outdoor
24 dBm (250 mW)
30 dBm
Indoor or outdoor
30 dBm (1 W)
36 dBm

Allowed Use
2.4 GHz ISM
Indoor or outdoor
20 dBm
Indoor only
23 dBm
Indoor only
23 dBm
Extended Indoor or outdoor
30 dBm

1.2 Describe the impact of various wireless technologies

1.2.                      Describe the impact of various wireless technologies
802.11 wireless LANs use unlicenced spectrum and therefore the signals can be affected by other devices and technologies that also use this spectrum. Wireless communication is generally divided into a number of categories, wireless LAN (WLAN) being the one we are mostly interested in but the others are Wireless Personal Area Networks (WPAN), Wireless Metropolitan Area Networks (WMAN) and Wireless Wide Area Networks (WWAN).

The spectrum allocated to 802.11 is in two bands, in the 2.4GHz and 5GHz range.

WPAN - a WPAN uses low-powered transmitters to create a network with a very short range, usually 20 to 30 feet (7 to 10 meters). WPANs are based on the IEEE 802.15 standard and include technologies like Bluetooth and ZigBee, although ZigBee can have a greater range.
WMAN - A wireless service over a large geographic area, such as all or a portion of a city. One common example, WiMAX, is based on the IEEE 802.16 standard. Licensed frequencies are commonly used although the specification does include use of the ISM band. No commercial deployments of WiMAX use the ISM band and for this reason is not a source of interference for wireless LANs.
WWAN - A wireless data service for mobile phones that is offered over a very large geographic area (regional, national, and even global) by telecommunications carriers. Licensed frequencies are used. Examples are 2G, 3G and 4G (LTE) mobile carrier networks. WWANs do not use the same frequencies as 802.11 and therefore are not a source of interference.
                                 1.2.1.      Bluetooth
Bluetooth is a PAN technology, used mainly for telephony headsets and file transfer. Found on most laptops, tablets and mobile phones. Bluetooth has low power consumption, requires line of sight and has good security, making it a good choice for mobile, battery-powered devices.

Bluetooth developed by the Bluetooth Special Interest Group and was incorporated into the IEEE 802.15.1 standard, but that standard is no longer maintained.

Devices operate in the 2.4-GHz ISM band (2.402 to 2.480Ghz), but are not compatible with the 802.11 standard. Bluetooth uses a frequency hopping spread spectrum (FHSS) technique, with devices moving through a predefined sequence of 79 channels with a bandwidth of 1 MHz each.

Class 3 radios – have a range of up to 1 meter or 3 feet, power is 1mW
Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 33 feet, 2.5mW power
Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet, power is 100mW

Up to eight devices can be paired or linked into a PAN, with one device taking a master role and the others operating as slaves.

Bluetooth transmitters could potentially interfere with the majority of the 2.4-GHz band because their channels overlap with the three non-overlapping 802.11 channels but only at a close range because of their low transmit power. If there are many Bluetooth devices in an 802.11 cell, they can create a saturation effect.

                                 1.2.2.      WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is a wireless technology designed to provide “last mile” broadband access to consumers within a geographic area and defined in the IEEE 802.16 standard. WiMAX does not require line of sight and can provide connection up to 3 to 10-km.
WiMAX operates in several bands between 2 and 11 GHz and from 10 to 66 GHz and can possibly interfere with 802.11 devices, but such interference is highly unlikely. No widely deployed solutions use the ISM bands; the systems that are advertised for ISM are not supported by any major WiMAX players.
                                 1.2.3.      ZigBee
ZigBee is wireless mesh LAN technology that uses relatively low power consumption and low data rates (20 to 250 Kbps). As a result, it offers reliable communication. ZigBee is commonly used for energy management and home and building automation applications.
ZigBee is defined in the IEEE 802.15.4 standard. It allocates the 2.4-GHz ISM band into 16 channels of 5 MHz each. Even though ZigBee uses the same band as 802.11 devices, it has a low duty cycle.
                                 1.2.4.      Cordless phone

Cordless phones use several wireless technologies to connect remote handsets to a central base station, using TDMA and FDMA techniques. Phones operating in the 2.4- and 5.8-GHz bands can cause significant interference with nearby WLANs. Cordless phones can use one channel at a time, but can also change channels dynamically. As well, transmit power levels can rise up to 250 mW, overpowering an AP at maximum power however they typically do not use the ISM band.

Thursday, June 4, 2015

1.4.1 Antenna types

There are a number of types of antenna used for wireless LANs. Generally they can be categorised as omnidirectional versus directional, indoor or outdoor. Many modern indoor APs have internal omnidirectional antennas. For point to point deployments, directional antennas are used. The provide high gain and are design for the outdoor environment. Examples of outdoor directional antennas are Yagi, patch, dish and mesh.


Omnidirectional antennas are design to transmit and receive signals in all directions equally (although less so along the axis of the antenna). The rubber-ducky antenna is a common example of an omnidirectional antenna.

Antennas are passive gain devices, in other words they concentrate a signal in certain directions but the overall power output is never more than the input power. Antenna gain is compare to a theoretical isotropic antenna which radiate signal in a perfect sphere. A dipole omnidirectional antenna will generally have a gain of about 2.15dBi.Its radiation pattern will be squashed in the vertical plane (usually desibed as doughnut shaped).

Directional Antennas

Directional antennas focus the energy and therefore have a higher gain than omnidirectional antennas. They are used for indoor areas such as hallways and in warehouses to direct the signal between racking.

Antennas are designated by their beamwidth. This describes how focused the energy is in the vertical plane and is calculated as the range between the half power points i.e. the points where the power output is half that of the maximum power.

1.3 Describe wireless regulatory bodies, standards, and certifications


The FCC is the regulatory body that exists in the United States and several other countries in the Americas. The FCC regulates RF frequencies, channels, and transmission power. The FCC has designated two frequency bands to be used for wireless networks, frequencies lie in the the 2.4Ghz and 5GHz bands.

ISM: 2.4–2.5-GHz
U-NII-1 (Band 1): 5.15 to 5.25 GHz
U-NII-2 (Band 2): 5.25 to 5.35 GHz
U-NII-2 Extended (Band 3): 5.47 to 5.725 GHz
U-NII-3 (Band 4): 5.725 to 5.825 GHz (also allocated as ISM)


The European Telecommunications Standards Institute (ETSI) is the European equivalent to the FCC.
Other countries have different regulatory bodies.

The bands allocated by ETSI are similar to the bands allocated by FCC however U-NII-3 is not available as it is a licenced spectrum.


The Institute of Electric and Electronic Engineers maintains the industry standards that are used for wireless LANs, among many others.

The most relevant IEE defined protocols in relation to wireless is 802.11 (Wireless LANs) and 802.15 (Personal area networks such as Bluetooth and Zigbee).

A thorough understanding of 802.3 (Ethernet) is also required.

WiFi Alliance

The Wi-Fi Alliance is a nonprofit industry association made up of wireless manufacturers around the world, all devoted to promoting wireless use. The WiFi Alliance provides a number of certification programs through which vendors of WiFi devices (Access Point and end user devices) can ensure their devices are compatible.

Trivial File transfer Protocol (TFTP)

Trivial File Transfer Protocol (TFTP) is a simple, lock-step, File Transfer Protocol which allows a Client (computing) to get from or put a file onto a remote Host (network). One of its primary uses is in the early stages of nodes booting from a Local Area Network. TFTP has been used for this application because it is very simple to implement. TFTP lacks security and most of the advanced features offered by more robust file transfer protocols such as File Transfer Protocol. TFTP uses UDP port 69.

The WCS includes a TFTP to store images for controller upgrades, backups of controller configuration files. An external TFTP server can also be used.

If you want to convert an AP from lightweight to standalone, you can do so via the command-
line interface (CLI) or by resetting the AP to factory defaults. If you do it from the
CLI, you use the following command:

archive download-sw /overwrite /force-reload { tftp:|ftp:}//location/

If you are resetting to factory defaults, use the mode button by holding it down until the
LED turns red. This causes the AP to reboot, ignoring its lightweight code, apply an IP address
of, and broadcast for an IOS file. This means you need a TFTP server on that
subnet and a default file on there with the naming convention cplatform_name-k9w7-

Cisco Discovery Protocol (CDP)/Link Layer Discovery Protocol (LLDP)

Cisco Discovery Protocol (CDP)/Link Layer Discovery Protocol (LLDP)

CDP is a Cisco proprietary layer 2 protocol used between directly connected devices. LLDP is a vendor neutral IEEE standard (IEEE 802.1AB) to perform similar functions.

Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc every 60 seconds by default. Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. By default information is aged out of the table after 180 seconds unless refreshed.

Cisco wired IP phones perform an intelligent exchange of information between the phone and the
switchport it is plugged into using Cisco Discovery Protocol (CDP). When the switch discovers a Cisco
IP phone, it can extend QoS trust to it dynamically. CDP can be enabled on Cisco wireless phones via Communications Manager.

Cisco recommends that you disable Cisco Discovery Protocol on the controller and access point when connected to non-Cisco switches as CDP is unsupported on non-Cisco switches and network elements.

By default, CDP is disabled on radio interfaces on indoor (nonindoor mesh) access points.

LLDP information is sent by devices from each of their interfaces at a fixed interval, to a series of multicast addresses. Information is stored and can be queried via SNMP. 

If an AP is configured for DHCP, then you can use CDP/LLDP to find out what IP address it has been given by showing the CDP neighbours on the switch to which the AP is connected.

Wednesday, June 3, 2015

NTP (Network Time Protocol)

NTP is a networking protocol design to synchronise clocks from time sources over networks. The NTP protocol is designed to handle the variability of latency in local and wide area networks.

NTP uses a client-server model with time messages sent via UDP on port 123. The current protocol is version 4 (NTPv4), which is a proposed standard as documented in RFC 5905.

NTP uses a hierarchical, semi-layered system of time sources. Each level of this hierarchy is termed a "stratum" and is assigned a number starting with zero at the top.

Stratum 0 

These are high-precision timekeeping devices such as atomic (cesium, rubidium) clocks, GPS clocks or other radio clocks.

Generally it is considered best practice for a client to poll three or more servers and determine the best source of time messages based on returned timestamps.

The Wireless LAN Controller (WLC) requires setting the system time. Once the time is set it will be maintained until a system reset. Using NTP to manage the time on the WLC is preferable. For lightweight APs the time is synchronised to the WLC time. For autonomous APs the time can be set manually.

How to configure time on Autonomous APs

How to configure NTP and SNTP on the Cisco AP

CCNA Wireless Certification - syllabus

Implementing Cisco Unified Wireless Networking Essentials (640-722)

Exam Description: The “Implementing Cisco Unified Wireless Network Essential” (IUWNE) v2.0 640- 722 exam is a 90-minute test with 60–70 questions that are associated with the Cisco CCNA® Wireless certification. This exam tests a candidate's knowledge of installing, configuring, operating, and troubleshooting small to medium-size WLANs.

The following topics are general guidelines for the content that is likely to be included on the exam.
However, other related topics may also appear on any specific instance of the exam. To better reflect the contents of the exam and for clarity purposes, these guidelines may change at any time without notice.

1.       Describe WLAN Fundamentals 20%
1.1   Describe basics of spread spectrum technology
1.2.1          Bluetooth
1.2.2          WiMAX
1.2.3          ZigBee
1.2.4          Cordless phone
1.3.1          FCC
1.3.2          ETSI
1.3.3          802.11a/b/g/n
1.3.4          WiFi Alliance
1.4   Describe WLAN RF principles
1.4.1          Antenna types
1.4.2          RF gain/loss
1.4.3          EIRP
1.4.4          Refraction
1.4.5          Reflection
1.5   Describe networking technologies that are used in wireless
1.5.1          SSID to WLAN_ID to interface to VLAN
1.5.2          802.1q trunking
1.6   Describe wireless topologies
1.6.1          IBSS
1.6.2          BSS
1.6.3          ESS
1.6.4          Point-to-point
1.6.5          Point-to-multipoint
1.6.6          Mesh
1.6.7          Bridging
1.7   Describe 802.11 authentication and encryption methods
1.7.1          Open
1.7.2          Shared
1.7.3          802.1X
1.7.4          EAP
1.7.5          TKIP
1.7.6          AES
1.8   Describe frame types
1.8.1          Associated and unassociated
1.8.2          Management
1.8.3          Control
1.8.4          Data
1.9   Describe basic RF deployment considerations related to site survey design of data or VoWLAN applications
1.9.1          Common RF interference sources such as devices, building material, AP location
1.9.2          Basic RF site survey design related to channel reuse, signal strength, and cell overlap
1.9.3          DNS
1.9.4          DHCP
1.9.5          TFTP
1.9.6          NTP
1.9.7          CDP/LLDP

2         Install a Basic Cisco Wireless LAN 17%
2.1   Identify the components of the Cisco Unified Wireless Network architecture
2.1.1          Split MAC
2.1.2          LWAPP
2.1.3          Standalone AP versus controller-based AP
2.1.4          Specific hardware examples
2.2   Install and configure autonomous access points in the small business environment
2.3   Describe the modes of controller-based AP deployment
2.3.1          Local
2.3.2          Monitor
2.3.3          HREAP
2.3.4          Sniffer
2.3.5          Rogue detector
2.3.6          Bridge
2.3.7          OEAP
2.3.8          SE-Connect
2.4   Describe controller-based AP discovery and association
2.4.1          DHCP
2.4.2          DNS
2.4.3          Master-Controller
2.4.4          Primary-Secondary-Tertiary
2.4.5          n+1 redundancy
2.5   Describe roaming
2.5.1          Layer 2 and Layer 3
2.5.2          Intracontroller and intercontroller
2.5.3          Mobility list
2.6   Configure a WLAN controller and access points
2.6.1          WLC: Ports, interfaces, WLANs, NTP, CLI and Web UI, CLI wizard, and LAG
2.6.2          AP: Channel and Power
2.7   Describe RRM fundamentals including ED-RRM
2.8   Verify basic wireless network operation

3         Install Wireless Clients 15%
3.1   Describe client WLAN configuration requirements, such as SSID, security selection, and authentication
3.2   Identify basic configuration of common wireless supplicants
3.2.1          Macintosh
3.2.2          Intel Wireless Pro
3.2.3          Windows
3.2.4          iOS
3.2.5          Android
3.3   Describe basic Cisco AnyConnect 3.0 or above wireless configuration parameters
3.4   Identify capabilities available in Cisco Unified CCX versions 1 through 5

4         Implement Basic WLAN Security 19%
4.1   Describe the general framework of wireless security and security components
4.1.1          Authentication
4.1.2          Encryption
4.1.3          MFP
4.1.4          IPS
4.2   Describe the evolution of supported authentication methods
4.2.1          PSK
4.2.2          802.1X including EAP-TLS, EAP-FAST, PEAP, LEAP, and WPA/WPA2
4.3   Configure the different sources of authentication
4.3.1          EAP local or EAP external
4.3.2          RADIUS
4.4   Configure authentication and encryption methods on a WLAN
4.4.1          WPA/WPA2 with PSK and 802.1x
4.5   Implement wireless guest networking

5         Operate Basic WCS 17%
5.1   Identify key functions of the Cisco WCS and Navigator (versions and licensing)
5.2   Navigate the WCS interface
5.3   Configure controllers and access points (APs)
5.3.1          Using the configuration tab, not templates
5.4   Use preconfigured maps in the WCS
5.4.1          Adding, relocating, removing access points
5.4.2          Turn heat maps on/off
5.4.3          View client location
5.4.4          View CleanAir zones of influence
5.5   Use the WCS Monitor tab and alarm summary to verify WLAN operations
5.6   Generate standard WCS reports
5.6.1          Inventory
5.6.2          CleanAir
5.6.3          Client-related
5.6.4          AP-related
5.6.5          Utilization

6         Conduct Basic WLAN Maintenance and Troubleshooting 12%
6.1   6.1 Identify and use basic WLAN troubleshooting tools
6.1.1          WLC show debug
6.1.2          Logging for client to AP connectivity, AP-to-controller connectivity
6.2   Use the WCS client troubleshooting tool
6.3   Transfer logs, configuration files, and operating system images to and from the WLC via the GUI
6.4   Differentiate and use WLC and AP (autonomous and LAP) management access methods
6.4.1          Console port
6.4.2          CLI
6.4.3          Telnet
6.4.4          SSH
6.4.5          HTTP
6.4.6          HTTPS
6.4.7          Wired versus wireless management