CompTIA Network+ N10-008 Exam: A Simple Guide To Wireless Solutions and Issues

Objectives:
- Given a scenario, install and configure the appropriate wireless standards and technologies.
- Given a scenario, troubleshoot common wireless connectivity issues.

Topics:
Understanding Wireless Basics
Wireless Channels and Frequencies
Cellular Technology Access
Speed, Distance, and Bandwidth
Channel Bonding
MIMO/MU-MIMO/Directional/Omnidirectional
Antenna Ratings
Antenna Coverage
Establishing Communications Between Wireless Devices
Configuring the Wireless Connection
Troubleshooting Wireless Issues
Site Surveys
Factors Affecting Wireless Signals
Interference
Reflection, Refraction, and Absorption
Troubleshooting AP Coverage

This guide covers CompTIA Network+ objectives 2.4 and 5.4. For more information on the official Network+ exam topics, see the “About the Network+ Exam” section in the Introduction.
One of the bigger changes in the networking world since the Network+ exam first came into being is in wireless networking technologies. Networks of all shapes and sizes incorporate wireless segments into their networks. Home wireless networking has also grown significantly in the past few years.
Wireless networking enables users to connect to a network using radio waves instead of wires. Network users within range of a wireless access point (AP) can move around an office or any other location within range of a hotspot freely, without needing to plug into a wired infrastructure. The benefits of wireless networking clearly have led to its continued growth.

This guide explores the many facets of wireless networking, starting with some of the concepts and technologies that make wireless networking possible.

Understanding Wireless Basics
Given a scenario, install and configure the appropriate wireless standards and technologies.
1. How many nonoverlapping channels are supported by 802.11a?
2. What are the ranges the 802.11b and 802.11g standards operate in?
3. True or false: Linux users can use the iwconfig command to view the state of their wireless network.
4. What does WPA3-Personal enable which replaces pre-shared key (PSK) in WPA2-Personal?

Answers:

1. The 802.11a standard supports up to eight nonoverlapping channels.
2. The 802.11b and 802.11g standards operate in the 2.4 to 2.497 GHz range.
3. True. Linux users can use the iwconfig command to view the state of their wireless network.
4. For better password protection, WPA3-Personal uses Simultaneous Authentication of Equals (SAE), which replaces pre-shared key (PSK) in WPA2-Personal.

Wireless Channels and Frequencies
Radio frequency (RF) channels are an important part of wireless communication. A channel is the band of RF used for the wireless communication. Each IEEE wireless standard specifies the channels that can be used. The 802.11a standard specifies radio frequency ranges between 5.15 and 5.875 GHz. In contrast, 802.11b and 802.11g standards operate in the 2.4 to 2.497 GHz range. 802.11n (known as Wi-Fi 4) can operate in either 2.4 GHz or 5 GHz ranges, and 802.11ac (known as Wi-Fi 5) operates in the 5 GHz range, while 802.11ax (known as Wi-Fi 6) can use 2.4 GHz or 5 GHz ranges. There has been much discussion about Wi-Fi congestion and the need for regulatory intervention, particularly in the 2.4 GHz range, but the regulatory impact of such intervention has largely prevented attempts to limit the use of these channels.
As of this writing, a standard for Wi-Fi 6e (the e is for extended) has been designated to support the higher 6 GHz standard, but it is not yet in use.
Hertz (Hz) is the standard of measurement for radio frequency. Hertz is used to measure the frequency of vibrations and waves, such as sound waves and electromagnetic waves. One hertz is equal to one cycle per second. RF is measured in kilohertz (KHz), one thousand cycles per second; megahertz (MHz), one million cycles per second; or gigahertz (GHz), one billion cycles per second.
As far as channels are concerned, 802.11a has a wider frequency band, enabling more channels and therefore more data throughput. As a result of the wider band, 802.11a supports up to eight nonoverlapping channels. 802.11b/g standards use the smaller band and support only up to three nonoverlapping channels.
It is recommended that nonoverlapping channels be used for communication. In the United States, 802.11b/g standards use 11 channels for data communication, as mentioned; three of these—channels 1, 6, and 11—are nonoverlapping. Most manufacturers set their default channel to one of the nonoverlapping channels to avoid transmission conflicts. With wireless devices you can select which channel your WLAN operates on to avoid interference from other wireless devices that operate in the 2.4 GHz frequency range.
When troubleshooting a wireless network, be aware that overlapping channels can disrupt the wireless communications. For example, in many environments, APs are inadvertently placed close together—perhaps two APs in separate offices located next door to each other or between floors. Signal disruption results if channel overlap exists between the APs. The solution is to try to move the AP to avoid the overlap problem, or to change channels to one of the other nonoverlapping channels. For example, you could switch from channel 6 to channel 11.
Typically, you would change the channel of a wireless device only if it overlapped with another device. If a channel must be changed, it must be changed to another, nonoverlapping channel.

As such, you can think of 802.11n as an amendment that improved upon the previous 802.11 standards by adding multiple input, multiple output (MIMO) antennas and a huge increase in the data rate. 802.11n devices are still available, but they have largely been superseded today by 802.11ac, which became an approved standard in January 2014, and 802.11ax (which uses MU-MMO and is discussed later). Both 802.11ac and 802.11ax can be thought of as extensions of 802.11n.

When troubleshooting a wireless problem in Windows, you can use the ipconfig command to see the status of IP configuration. Similarly, the ifconfig command can be used in Linux. In addition, Linux users can use the iwconfig command to view the state of your wireless network. Using iwconfig, you can view such important information as the link quality, AP MAC address, data rate, and encryption keys, which can be helpful in ensuring that the parameters in the network are consistent.
IEEE 802.11b/g wireless systems communicate with each other using radio frequency signals in the band between 2.4 GHz and 2.5 GHz. Neighboring channels are 5 MHz apart. Applying two channels that allow the maximum channel separation decreases the amount of channel crosstalk and provides a noticeable performance increase over networks with minimal channel separation.

When you’re deploying a wireless network, it is recommended that you use channel 1, grow to use channel 6, and add channel 11 when necessary, because these three channels do not overlap.
The 802.11n, 802.11ac, and 802.11ax standards are the most common today, and you will be hard-pressed to purchase (or even find) older technologies. It is, however, recommended that you know the older technologies for the exam.

TABLE: RF Channels for 802.11b/g/n/ax

When looking at the table below, remember that the RF channels listed (2412 for channel 1, 2417 for 2, and so on) are actually the center frequency that the transceiver within the radio and AP uses. There is only a 5 MHz separation between the center frequencies, and an 802.11b signal occupies approximately 30 MHz of the frequency spectrum. As a result, data signals fall within about 15 MHz of each side of the center frequency and overlap with several adjacent channel frequencies. This leaves you with only three channels (channels 1, 6, and 11 for the United States) that you can use without causing interference between APs.

TABLE: RF Channels for 802.11a/ac/ax

As mentioned, channels 1, 6, and 11 do not overlap. On a non-MIMO setup (such as with 802.11a, b, or g), always try to use one of these three channels. Similarly, if you use 802.11n/ac/ax with 20 MHz channels, stay with channels 1, 6, and 11 to be safe even though 802.11ac and ax channels can be 20 MHz, 40 MHz, 80 MHz, and 160 MHz wide.
Understand the importance of channels 1, 6, and 11 as you study for the exam.

It is important to note that 802.11ac operates in the 5 GHz range only, while 802.11ax operates in both the 2.4 GHz and 5 GHz ranges (which no other standard had done since 802.11n) and is, thus, compatible with 802.11a/b/g/n/ac. Operating in both ranges creates more available channels (early chipsets, for example, support eight channels in the 5 GHz and four channels in the 2.4 GHz range for a total of twelve available channels). With 802.11ac, MU-MIMO is limited to only downlink transmissions while 802.11ax creates MU-MIMO connections so a downlink MU-MIMO access point can transmit concurrently to multiple receivers and an uplink MU-MIMO endpoint can simultaneously receive from multiple transmitters.
The 802.11ax standard will support up to eight MU-MIMO transmissions at a time (an increase from the four available with 802.11ac). Orthogonal frequency-division multiple access (OFDMA) is new with 802.11ax (and discussed in the upcoming section on channel bonding), as are several other technologies (including trigger-based random access, dynamic fragmentation, and spatial frequency reuse) enabling it to have a theoretical maximum speed of 10 Gbps. New with 802.11ax is the use of 1024-QAM (quadrature amplitude modulation) to encode (modulate/demodulate) a larger number of data bits and increase throughput.
A subcategory of 802.11ax, known as Wi-Fi 6e (Wi-Fi 6 extended), is expected to be available and adopted soon and will also work in the 6 GHz frequency: devices that are compatible will be able to operate on the 2.4, 5, and 6 GHz frequencies and benefit from less congested bands.

Cellular Technology Access
One reason why cellular access is an important topic from the perspective of this exam is that when devices (smartphones, tablets, etc.) are accessing the network outside of a Wi-Fi connection, they are often doing so through a cellular network and that cellular network becomes the WAN. As a network administrator, you are dependent upon the cellular network your users are using (and the security, or lack thereof, inherent in it) to protect your data and resources.

The Global System for Mobile Communications (GSM) initially used time-division multiple access (TDMA) to provide multiuser access by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals and, ideally, this happens so quickly that the user is unaware of it. TDMA was replaced in later implementations by code-division multiple access (CDMA) which (instead of splitting the channel into time slices) uses different frequencies for each user to provide various means of cell phone coverage.
The individual methods that can be used for cellular access include 5G, LTE/4G, or 3G, and they represent enhancements to the technology over time—each generation represents new frequency bands and higher data rates. The original GSM access (with both TDMA and CDMA) was labeled 2G. As standards that became available focused on increasing speeds and enabling sending of images, this morphed into 3G (which, initially, was more marketing hype than anything else). 4G added the capability to implement mobile broadband Internet access (not just for smartphones but also laptops with wireless modems and other similar devices). LTE (Long-Term Evolution) was based on EDGE (Enhanced Data rates for GSM Evolution) and HSPA (high-speed packet access) technologies, which increased the capacity and speed by using a different radio interface together with core network improvements. The newest iteration, 5G, not only provides faster speeds but is also needed to meet the needs of Internet of Things (IoT) sensors and other communication-intensive devices.

For purposes of comparison, a typical download speed of basic 3G would be 0.0375 Mbps; 4G would be 150 Mbps; LTE would be approximately 600 Mbps; and 5G is estimated to be between 1–10 Gbps.

Speed, Distance, and Bandwidth
When talking about wireless transmissions, you need to distinguish between throughput and data rate. From time to time these terms are used interchangeably, but technically speaking, they are different. As shown later in this guide, each wireless standard has an associated speed. For instance, 802.11n lists a theoretical speed of up to 600 Mbps, and 802.11ax has a theoretical maximum speed of a whopping 10 Gbps. This represents the speed at which devices using this standard can send and receive data. However, in network data transmissions, many factors prevent the actual speeds from reaching this end-to-end theoretical maximum. For instance, data packets include overhead such as routing information, checksums, and error recovery data. Although this might all be necessary, it can impact overall speed.
The number of clients on the network can also impact the data rate; the more clients, the more collisions. Depending on the network layout, collisions can have a significant impact on end-to-end transmission speeds. Wireless network signals degrade as they pass through obstructions such as walls or doors; the signal speed deteriorates with each obstruction.
All these factors leave you with the actual throughput of wireless data transmissions. Goodput represents the actual speed to expect from wireless transmissions (what is often thought of as throughput). In practical applications, wireless transmissions are approximately one-half or less of the data rate. Depending on the wireless setup, the transmission rate could be much less than its theoretical maximum.
Data rate refers to the theoretical maximum of a wireless standard, such as the 600 Mbps for 802.11n or the 10 Gbps for 802.11ax. Throughput refers to the actual speeds achieved after all implementation and interference factors.
Speed is always an important factor in the design of any network, and high throughput (ht) is a goal that has been around for a while. A number of the 802.11 standards offer a high throughput connection type, such as 802.11a-ht and 802.11g-ht. Although these implementations are better with the ht than without, it is true that today you will achieve better results with 802.11ax.

Channel Bonding
With channel bonding, you can use two channels at the same time. As you might guess, the ability to use two channels at once increases performance. Bonding can help increase wireless transmission rates with 802.11n from a maximum of 40 MHz up to 80 or even 160 MHz (for speed increases of 117 or 333 percent, respectively). 802.11n uses the orthogonal frequency-division multiplexing (OFDM) transmission strategy.
Whereas 802.11n stopped at four spatial streams, 802.11ac goes to eight (for another 100 percent speed increase). 802.11ax replaces OFDM with OFDMA, a multi-user version of OFDM that uses a digital modulation scheme. The multiple access is achieved by assigning subsets of subcarriers to individual users.
If it seems as if 802.11ax keeps coming up in each discussion, the reason is that it is important to know this standard for the exam. Know that it works in both bands (2.4 and 5 GHz), utilizes multiuser MIMO (downlink and uplink), OFDMA (downlink and uplink), and higher data rates (thanks to 1024-QAM).

MIMO/MU-MIMO/Directional/Omnidirectional
A wireless antenna is an integral part of overall wireless communication. Antennas come in many shapes and sizes, with each one designed for a specific purpose. Selecting the right antenna for a particular network implementation is a critical consideration, and one that could ultimately decide how successful a wireless network will be. In addition, using the right antenna can save you money on networking costs because you need fewer antennas and APs.
Multiple input, multiple output (MIMO) and multiuser multiple input, multiple output (MU-MIMO) are advanced antenna technologies that are key in wireless standards such as 802.11n, 802.11ac, 802.11ax, and LTE.
Many small home network adapters and APs come with a nonupgradable antenna, but higher-grade wireless devices require you to choose an antenna. Determining which antenna to select takes careful planning and requires an understanding of what range and speed you need for a network.

The antenna is designed to help wireless networks do the following:
Work around obstacles
Minimize the effects of interference
Increase signal strength
Focus the transmission, which can increase signal speed

The following sections explore some of the characteristics of wireless antennas.

Antenna Ratings
When a wireless signal is low and is affected by heavy interference, it might be possible to upgrade the antenna to create a more solid wireless connection. To determine an antenna’s strength, refer to its gain value. But how do you determine the gain value?
For the exam, know that an antenna’s strength is its gain value.
Suppose that a huge wireless tower is emanating circular waves in all directions. If you could see these waves, you would see them forming a sphere around the tower. The signals around the antenna flow equally in all directions, including up and down. An antenna that does this has a 0 dBi gain value and is called an isotropic antenna. The isotropic antenna rating provides a base point for measuring actual antenna strength.
The dB in dBi stands for decibels, and the i stands for the hypothetical isotropic antenna.
An antenna’s gain value represents the difference between the 0dBi isotropic and the antenna’s power. For example, a wireless antenna advertised as 15dBi is 15 times stronger than the hypothetical isotropic antenna. The higher the decibel figure, the higher the gain.
When looking at wireless antennas, remember that a higher gain value means stronger send and receive signals. In terms of performance, the general rule is that every 3dB of gain added doubles an antenna’s effective power output.

Antenna Coverage
When selecting an antenna for a particular wireless implementation, you need to determine the type of coverage the antenna uses. In a typical configuration, a wireless antenna can be either omnidirectional or directional (also called unidirectional). Which one you choose depends on the wireless environment.
An omnidirectional antenna is designed to provide a 360-degree dispersed wave pattern. This type of antenna is used when coverage in all directions from the antenna is required. Omnidirectional antennas are advantageous when a broad-based signal is required. For example, if you provide an even signal in all directions, clients can access the antenna and its associated AP from various locations. Because of the dispersed nature of omnidirectional antennas, the signal is weaker overall and therefore accommodates shorter signal distances. Omnidirectional antennas are great in an environment that has a clear line of sight between the senders and receivers. The power is evenly spread to all points, making omnidirectional antennas well suited for home and small office applications.
Directional antennas are designed to focus the signal in a particular direction (which is why they are often referred to as unidirectional). This focused signal enables greater distances and a stronger signal between two points. The greater distances enabled by directional antennas give you a viable alternative for connecting locations, such as two offices, in a point-to-point configuration.
Directional antennas are also used when you need to tunnel or thread a signal through a series of obstacles. This arrangement concentrates the signal power in a specific direction and enables you to use less power for a greater distance than an omnidirectional antenna.

TABLE: Comparing Omnidirectional and Directional Antennas

The directional wireless range can be increased and decreased.
Omnidirectional antennas are limited to their circular pattern range. Directional antennas can be adjusted to define a specific pattern, wider or more focused.

In the wireless world, polarization refers to the direction in which the antenna radiates wavelengths. This direction can be vertical, horizontal, or circular. Today, vertical antennas are perhaps the most common. As far as the configuration is concerned, the sending and receiving antennas should be set to the same polarization.
Omnidirectional antennas provide wide coverage but weaker signal strength in any one direction than a directional antenna.

Establishing Communications Between Wireless Devices
When you work with wireless networks, you must have a basic understanding of the communication that occurs between wireless devices. If you use an infrastructure wireless network design, the network has two key parts: the wireless client, also known as the station (STA), and the AP. The AP acts as a bridge (or wireless bridge) between the STA and the wired network.

When a single AP is connected to the wired network and to a set of wireless stations, it is called a basic service set (BSS). An extended service set (ESS) describes the use of multiple BSSs that form a single subnetwork. Ad hoc mode is sometimes called an independent basic service set (IBSS).
As with other forms of network communication, before transmissions between devices can occur, the wireless AP and the client must begin to talk to each other. In the wireless world, this is a two-step process involving association and authentication.
The association process occurs when a wireless adapter is turned on. The client adapter immediately begins scanning the wireless frequencies for wireless APs or, if using ad hoc mode, other wireless devices. When the wireless client is configured to operate in infrastructure mode, the user can choose a wireless AP with which to connect. This process may also be automatic, with the AP selection based on the SSID, signal strength, and frame error rate. Finally, the wireless adapter switches to the assigned channel of the selected wireless AP and negotiates the use of a port.
If at any point the signal between the devices drops below an acceptable level, or if the signal becomes unavailable for any reason, the wireless adapter initiates another scan, looking for an AP with stronger signals. When the new AP is located, the wireless adapter selects it and associates with it. This is known as reassociation.

The 802.11 standards enable a wireless client to roam between multiple APs. An AP transmits a beacon signal every so many milliseconds. It includes a time stamp for client synchronization and an indication of supported data rates. A client system uses the beacon message to identify the strength of the existing connection to an AP. If the connection is too weak, the roaming client attempts to associate itself with a new AP. This association enables the client system to roam between distances and APs.
With the association process complete, the authentication process begins. After the devices associate, keyed security measures are applied before communication can take place. On many APs, authentication can be set to either shared key authentication or open authentication. The default setting for older APs typically is open authentication. Open authentication enables access with only the SSID and/or the correct WEP key for the AP. The problem with open authentication is that if you do not have other protection or authentication mechanisms in place, your wireless network is totally open to intruders. When set to shared key mode, the client must meet security requirements before communication with the AP can occur.
After security requirements are met, you have established IP-level communication. This means that wireless standard requirements have been met, and Ethernet networking takes over. There is basically a switch from 802.11 to 802.3 standards. The wireless standards create the physical link to the network, enabling regular networking standards and protocols to use the link. This is how the physical cable is replaced, but to the networking technologies there is no difference between regular cable media and wireless media.
Several components combine to enable wireless communications between devices. Each of these must be configured on both the client and the AP:
- Service set identifier (SSID): Whether your wireless network uses infrastructure mode or ad hoc mode, an SSID is required. The SSID is a configurable client identification that enables clients to communicate with a particular base station. Only client systems configured with the same SSID as the AP can communicate with it. SSIDs provide a simple password arrangement between base stations and clients in a BSS network. ESSIDs are used for the ESS wireless network.
Wireless channel: As stated earlier in this guide, RF channels are an important part of wireless communications. A channel is the frequency band used for the wireless communication. Each standard specifies the channels that can be used. The 802.11a standard specified radio frequency ranges between 5.15 GHz and 5.875 GHz. In contrast, the 802.11b and 802.11g standards operate in the 2.4 GHz to 2.497 GHz ranges. 802.11n and 802.11ax can operate in either the 2.4 GHz or 5 GHz range, and 802.11ac is at 5 GHz. Fourteen channels are defined in the IEEE 802.11 channel set, 11 of which are available in North America.
- Security features: IEEE 802.11 provides security using two methods: authentication and encryption. Authentication verifies the client system. In infrastructure mode, authentication is established between an AP and each station. Wireless encryption services must be the same on the client and the AP for communication to occur.

Wireless devices ship with default SSIDs, security settings, channels, passwords, and usernames. To protect yourself, it is strongly recommended that you change these default settings. Today, many Internet sites list the default settings used by manufacturers with their wireless devices. This information is used by people who want to gain unauthorized access to your wireless devices.

Configuring the Wireless Connection
Wireless connection configuration is fairly straightforward. The figure below shows an example of a simple wireless router. In addition to providing wireless access, it also includes a four-port wired switch.



A wireless broadband router for a small network

Most of the broadband routers similar to the one shown in Figure 6.1 differ based upon the following features:
- Wireless bands: The routers can provide only 2.4 GHz, only 5 GHz, or be either selectable (choosing one of the two) or simultaneous (using both).
Switch speed: The ports on the switch can usually support either Fast Ethernet (10/100 Mbps) or Gigabit Ethernet (10/100/1000 Mbps).
- Security supported: The SSID, security mode, and passphrase may be configurable for each band, and some routers include a push-button feature for accessing setup. Some enable you to configure MAC address filtering and guest access, such as the one shown below. MAC address filtering enables you to limit access to only those specified hosts. Guest access uses a different password and network name and enables visitors to use the Internet without having access to the rest of the network (thus avoiding your data and computers).



Configuring MAC address filtering on a SOHO router

Make sure that you understand the purpose of MAC address filtering.
- Antenna: The antenna may be a single external pole, two poles or even more, or be entirely internal. The model shown in Figure 6.1 uses an internal antenna, as shown below.



The antenna is the wire and metal component on the left

The wireless antenna for a laptop, all-in-one desktop system, or mobile device is often built in to the areas around the screen.
The settings for a wireless router are typically clearly laid out. You can adjust many settings for troubleshooting or security reasons. For example, most newer small office/home office (SOHO) wireless routers offer useful configuration setup screens for administering firewall, demilitarized zone (DMZ), apps and gaming, parental controls, guest access, and diagnostic settings (as illustrated in Figure 6.4). Following are some of the basic settings that can be adjusted on a wireless AP:
- SSID: This name is used for anyone who wants to access the Internet through this wireless AP. The SSID is a configurable client identification that enables clients to communicate with a particular base station. In an application, only clients configured with the same SSID can communicate with base stations having the same SSID. SSID provides a simple password arrangement between base stations and clients.



Common security configuration parameters for a wireless router

As far as troubleshooting is concerned, if a client cannot access a base station, you need to ensure that both use the same SSID. Incompatible SSIDs are sometimes found when clients move computers, such as laptops or other mobile devices, between different wireless networks. They obtain an SSID from one network. If the system is not rebooted, the old SSID does not enable communication with a different base station.
- Channel: To access this network, all systems must use this channel. If needed, you can change the channel using the drop-down menu. The menu lists channels 1 through 11.
- SSID broadcast: In their default configuration, wireless APs typically broadcast the SSID name into the air at regular intervals. This feature is intended to allow clients to easily discover the network and roam between WLANs. The problem with SSID broadcasting is that it makes it a little easier to get around security. SSIDs are not encrypted or protected in any way. Anyone can snoop and get a look at the SSID and attempt to join the network if not secured.

For SOHO use, roaming is not needed. This feature can be disabled for home use to improve the security of your WLAN. As soon as your wireless clients are manually configured with the right SSID, they no longer require these broadcast messages.
- Authentication: When configuring authentication security for the AP, you have several options depending on the age of the AP. At the lower (older) end, choices often include WEP-Open, WEP-Shared, and WPA-PSK. WEP-Open is the simplest of the authentication methods because it does not perform any type of client verification. It is a weak form of authentication because it requires no proof of identity. WEP-Shared requires that a WEP key be configured on both the client system and the AP. This makes authentication with WEP-Shared mandatory, so it is more secure for wireless transmission. To strengthen WEP encryption, a Temporal Key Integrity Protocol (TKIP) was employed. This protocol placed a 128-bit wrapper around the WEP encryption with a key that is based on things such as the MAC address of the destination device and the serial number of the packet. TKIP was designed as a backward-compatible replacement to WEP, and it could work with all existing hardware. Without the use of TKIP, WEP was considered weak. It is worth noting, however, that even TKIP has been broken.
 

- Wi-Fi Protected Access with Pre-Shared Key (WPA-PSK) is a stronger form of encryption in which keys are automatically changed and authenticated between devices after a specified period of time, or after a specified number of packets have been transmitted.
- Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP). CCMP uses 128-bit AES encryption with a 48-bit initialization vector. With the larger initialization vector, it increases the difficulty in cracking and minimizes the risk of a replay attack. WPA3 (shown below) uses Simultaneous Authentication of Equals (SAE), which replaces pre-shared key (PSK) used in WPA2-Personal and is resistant to offline dictionary attacks. When given as a choice, WPA3-Personal adds more protection for individual users as a result of the password-based authentication even when the passwords that users choose are not all that complex.



Newer wireless routers offer WPA2/WPA3 Mixed Personal mode as a security option

Know that WPA3 helps prevent offline password attacks by using Simultaneous Authentication of Equals. SAE allows users to choose easier-to-remember passwords and, through forward secrecy, does not compromise traffic already transmitted even if the password becomes compromised.
- Wireless mode: To access the network, the client must use the same wireless mode as the AP. Today, most users configure the network for 802.11ac or 802.11ax for faster speeds.
- DTIM period (seconds): Wireless transmissions can broadcast to all systems—that is, they can send messages to all clients on the wireless network. Multiple broadcast messages are known as multicast or broadcast traffic. Delivery Traffic Indication Message (DTIM) is a feature used to ensure that when the multicast or broadcast traffic is sent, all systems are awake to hear the message. The DTIM setting specifies how often the DTIM is sent within the beacon frame. For example, if the DTIM setting by default is 1, this means that the DTIM is sent with every beacon. If the DTIM is set to 3, the DTIM is sent every three beacons as a DTIM wake-up call.
Maximum connection rate: The transfer rate typically is set to Auto by default. This setting enables the maximum connection speed. However, it is possible to decrease the speed to increase the distance that the signal travels and boost signal strength caused by poor environmental conditions.
- Network type: This is where the network can be set to use the ad hoc or infrastructure network design.

It is easy to fall into the trap of thinking of wireless devices as being laptops connecting to the AP. Over the years, however, the number and type of mobile devices that need to connect to the network has expanded tremendously. In addition to the laptops and tablets, gaming devices, media devices, cell phones, and IoT devices now all connect for wireless access. Although they might all seem different, they require the same information to connect.
Unfortunately, they all bring security concerns as well. Bring-your-own-device (BYOD) policies are highly recommended for every organization. Administrators can implement mobile device management (MDM) and mobile application management (MAM) products to help with the management and administration issues with these devices.
Know that devices on networks today include such things as PCs, cell phones, laptops, tablets, gaming devices, media, and IoT devices.

Troubleshooting Wireless Issues
Given a scenario, troubleshoot common wireless connectivity issues.
1. You have noticed that connections between nodes on one network are inconsistent and suspect there may be another network using the same channel. What should you try first?
2. True or false: Weather conditions should not have a noticeable impact on wireless signal integrity.
3. True or false: When a client connects to an AP, it is said to associate with that AP, and disassociation is the process of it no longer associating with that AP.

Answers:
1. If connections are inconsistent, try changing the frequency channel to another, nonoverlapping channel.
2. False. Weather conditions can have a huge impact on wireless signal integrity.
3. True. When a client connects to an AP, it is said to associate with that AP, and disassociation is the process of it no longer associating with that AP. Disassociation can happen any time the AP thinks it no longer needs to communicate with the client.

Poor communication between wireless devices has many different potential causes. Some of these problems, such as latency and jitter, are similar to those that exist with wired connections and were discussed previously. Others are characteristic only of wireless connectivity and are discussed in the following sections.
To put a lot of information into a format that is coherent, the discussion starts with a review checklist of wireless troubleshooting and then moves into some individual topics:
- Signal loss: The cause of signal loss, known as attenuation, can be anything from distance to obstacles to interference. The signal-to-noise ratio should be examined to measure the desired signal against the background noise interfering with it. Look for signs of saturation with either the device or the bandwidth.
Signal-to-noise ratio can be used to measure that which the name implies.
- Wireless enabled: Some laptops make it incredibly easy to turn wireless on and off. A user may accidentally press a button that he is not aware of and then suddenly not be able to access the network. Although this is a simple problem to fix, it is one that you need to identify as quickly as possible. The figure below shows the wireless light on an HP laptop. This light is also a button that toggles wireless on and off. When the light is blue, wireless is enabled, and when it is not blue (orange), it is disabled.



A light also serves as a button, enabling wireless to be quickly turned on and off

Untested updates: Never apply untested updates to the network. This is especially true with AP updates, which should always be tested in nonproduction environments before being applied to live machines.
- Wrong wireless standard: Make sure that the standard you are using supports the rates and attributes you are striving for. This is particularly important in terms of throughput, frequency, distance, and channels.
- Auto transfer rate: By default, wireless devices are configured to use the strongest, fastest signal. If you experience connectivity problems between wireless devices, try using the lower transfer rate in a fixed mode to achieve a more stable connection. For example, you can manually choose the wireless transfer rate. Also, instead of using the highest transfer rate available, try a lesser speed. The higher the transfer rate, the shorter the connection distance.
- AP placement and configuration: If signal strength is low, try moving the AP to a new location. Moving it just a few feet can make a difference. You can also try to bounce a signal, as needed, off reflective surfaces. The configuration of the AP should take into account the use of Lightweight Access Point Protocol (LWAPP), which can allow you to monitor the network and reduce the amount of time needed to configure and troubleshoot it—and whether the authentication/configuration will be done at the AP (known as thick) or it will be passed on up (known as thin).
- Received Signal Strength Indication (RSSI). This value is an indicator of the power level being received by the receiving host after any antenna or cable loss. The greater the RSSI value, the stronger the signal.
Anytime an AP is doing key functions—authentication, filtering, QoS enforcement, and so on—it is said to be thick. If it is not doing these key functions—even though it might be doing others—it is usually said to be thin. Although there is no 100 percent sure method of distinguishing what a vendor will label thick or thin, one good rule is to question whether the AP is dependent on another device (thin) or not (thick).
- Antenna: The default antenna shipped with wireless devices may not be powerful enough for a particular client system. Better-quality antennas can be purchased for some APs, which can boost the distance the signal can go. Make sure you do not use the wrong antenna type or have other incompatibilities.
- Effective Isotropic Radiated Power (EIRP) is used to measure the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is the total power—expressed in watts—that would need to be radiated by a half-wave dipole antenna to give the same signal strength as the actual source antenna at a distant receiver located in the direction of the antenna’s strongest beam.
- Environmental obstructions: Wireless RF communications are weakened if they have to travel through obstructions such as metal studs, window film, and concrete walls. Wireless site surveys can be performed to troubleshoot RF signal loss issues as well as assist in planning optimal locations for new wireless networks.
- Conflicting devices: Any device that uses the same frequency range as the wireless device can cause interference. For example, 2.4 GHz phones, appliances, or Bluetooth devices can cause interference with devices using the 802.11g or single-band 802.11n wireless standards.
- Wireless channels: If connections are inconsistent, try changing the channel to another, nonoverlapping channel. Make certain you do not have mismatched channels between devices.
- Protocol issues: If an IP address is not assigned to the wireless client, a wrong SSID or incorrect WEP/WPA/WPA2/WPA3 settings can prevent a system from obtaining IP information.
- SSID: The SSID number used on the client system must match the one used on the AP. You might need to change it if you are switching a laptop or other wireless device between different WLANs.
- Encryption type: If encryption is enabled on the connecting system, the encryption type must match what is set in the AP. For example, if the AP uses WPA2/WPA3-AES, the connecting system must also use WPA2/WPA3-AES.
- Captive portal issues: Most public networks, including Wi-Fi hotspots, use a captive portal, which is a web page that requires users to agree to some condition before they use the network or Internet. The condition could be to agree to the acceptable use policy (AUP), payment charges for the time they are using the network, and so forth. Security vulnerabilities have been reported with captive portals, so administrators should be on the alert for any new problems that are reported.
Client disassociation issues: When a client connects to an AP, it is said to associate with that AP, and disassociation is the process of it no longer associating with that AP. Disassociation can happen any time the AP thinks it no longer needs to communicate with the client—due to going into hibernation mode, powering down, leaving the building, and so on. Most unintentional disassociations can be traced to weak signals, but relocating the AP (or boosting the signal) can often help.
Captive portals are common in public places such as airports and coffee shops. The user simply clicks Accept, views an advertisement, provides an email address, or performs some other required action. The network then grants access to the user and no longer holds the user captive to that portal.
Most router configuration interfaces allow you to run basic diagnostics through them, as illustrated below. You can also usually change the security settings and configure the firewall, as shown below.



Wireless router diagnostic options



Configuring security settings

Site Surveys
As more networks go wireless, you need to pay special attention to issues associated with them. Wireless survey tools can be used to create heat maps showing the quantity and quality of wireless network coverage in areas. They can also allow you to see access points (including rogues) and security settings. These tools can be used to help you design and deploy an efficient network, and they can also be used (by you or others) to find weaknesses in your existing network (often marketed for this purpose as wireless analyzers).

Factors Affecting Wireless Signals
Because wireless signals travel through the atmosphere, they are susceptible to different types of interference than are standard wired networks. Interference weakens wireless signals and therefore is an important consideration when working with wireless networking.

Interference
Wireless interference is an important consideration when you plan a wireless network. Interference is, unfortunately, inevitable, but the trick is to minimize the levels of interference. Wireless LAN communications typically are based on radio frequency signals that require a clear and unobstructed transmission path.

The following factors can cause interference:
- Physical objects: Trees, masonry, buildings, and other physical structures are some of the most common sources of interference. The density of the materials used in a building’s construction determines the number of walls the RF signal can pass through and still maintain adequate coverage. Concrete and steel walls are particularly difficult for a signal to pass through. These structures weaken or at times completely prevent wireless signals.
Be sure that you understand that physical objects are a common source of interference. A wireless site survey can be used to test for interference.
- Radio frequency interference: Wireless technologies such as 802.11n can use an RF range of 2.4 GHz, and so do many other devices, such as cordless phones, microwaves, Bluetooth devices, and so on. Devices that share the channel can cause noise and weaken the signals.
- Electrical interference: Electrical interference comes from devices such as computers, refrigerators, fans, lighting fixtures, or any other motorized devices. The impact that electrical interference has on the signal depends on the proximity of the electrical device to the wireless AP. Advances in wireless technologies and in electrical devices have reduced the impact that these types of devices have on wireless transmissions.
- Environmental factors: Weather conditions can have a huge impact on wireless signal integrity. Lightning, for example, can cause electrical interference, and fog can weaken signals as they pass through.

Reflection, Refraction, and Absorption
The line differentiating between interference and reflection can be blurry when it comes to wireless networking. The key difference between them is that interference is a conflict with something else (usually another signal), whereas reflection is a problem caused by a bouncing of the same signal off an object. A subset of this is refraction, which involves a change in direction of the wave as a result of its traveling at different speeds at different points. Put in simple terms, reflection happens when the signal hits a piece of metal and cannot pass through, and refraction happens when the signal goes through a body of water.
If the wave is completely swallowed by the object it hits (not reflected, or refracted), then it is said to be absorbed. Where security is concerned, items known to absorb wireless signals can be used to prevent the signal from traveling beyond an established perimeter. Shielding paint (sometimes called RF paint) can be used for this purpose, as can copper plates and aluminum sheets.
Many wireless implementations are found in the office or at home. Even when outside interference such as weather is not a problem, every office has plenty of wireless obstacles.

TABLE: Wireless Obstacles Found Indoors

Be sure that you understand the severity of obstructions given in the Table above.

Troubleshooting AP Coverage
Like any other network medium, APs have a limited transmission distance. This limitation is an important consideration when you decide where an AP should be placed on the network. When troubleshooting a wireless network, pay close attention to how far the client systems are from the AP.
Distance limitations from the AP are among the first things to check when troubleshooting AP coverage.
When faced with a problem in which client systems cannot consistently access the AP, you could try moving the AP to better cover the area, but then you may disrupt access for users in other areas. So what can be done to troubleshoot AP coverage?
Depending on the network environment, the quick solution may be to throw money at the problem and purchase another access point, cabling, and other hardware to expand the transmission area. However, you can try a few things before installing another wireless AP. The following list starts with the least expensive solution and progresses to the most expensive:
- Increase transmission power: Some APs have a setting to adjust the transmission power output (power levels). By default, most of these settings are set to the maximum output; however, this is worth verifying just in case. You can decrease the transmission power if you are trying to reduce the dispersion of radio waves beyond the immediate network. Increasing the power gives clients stronger data signals and greater transmission distances.
- Relocate the AP: When wireless client systems suffer from connectivity problems, the solution may be as simple as relocating the AP. You could relocate it across the room, a few feet away, or across the hall. Finding the right location will likely take a little trial and error.
- Adjust or replace antennas: If the AP distance is insufficient for some network clients, you might need to replace the default antenna used with both the AP and the client with higher-end antennas. Upgrading an antenna can make a big difference in terms of transmission range. Unfortunately, not all APs have replaceable antennas.
- Tweak the signal amplification: Radio frequency (RF) amplifiers add significant distance to wireless signals. An RF amplifier increases the strength and readability of the data transmission. The amplifier improves both the received and transmitted signals, resulting in an increase in wireless network performance.
- Use a repeater: Before installing a new AP, you might want to think about a wireless repeater. When set to the same channel as the AP, the repeater takes the transmission and repeats it. So, the AP transmission gets to the repeater, and then the repeater duplicates the signal and passes it on. This is an effective strategy to increase wireless transmission distances.
Be prepared to answer questions on AP coverage and possible reasons to relocate or replace APs.