Chapter 7
Describe Wireless Principles
Here is another important chapter in the Network Fundamentals section of the CCNA 200-301 exam blueprint from Cisco Systems. Wireless networking has become incredibly commonplace today, especially as more and more of us have become heavily dependent on cloud-based resources. For example, most students now use office suites accessed using a Web browser and cloud-based applications. For such an individual, Wi-Fi is the key to productivity. In fact, I am currently composing this book using an online version of Microsoft Word as I sit in my local coffee shop, enjoying the complimentary wireless signal that takes me to the Internet.
This chapter covers the following essential terms and components:
▸ Radio frequencies
▸ SSIDs
▸ Wi-Fi channel overlap
Topic: Describe wireless principles
CramSaver
If you can correctly answer these CramSaver questions, save time by skimming the ExamAlerts in this section and then completing the CramQuiz at the end of this section and the Review Questions at the end of the chapter. If you are in doubt at all, read everything in this chapter!
1. What two RF bands are most commonly in use today for Wi-Fi communications?
_________
2. What are the non-overlapping channels in the 2.4 GHz RF band?
_________
Remember that wireless technologies send data by using ranges of radio frequencies (RF) rather than physical cables. A range of frequencies is typically called a band. Do you remember AM radio? It operates using 530 kHz to 1710 kHz, known as the AM band.
You should know about two main bands that are used for wireless: the 2.4 GHz band and the 5 GHz band. You often see these bands included in wireless AP SSID names. For example, your AP might provide the default names CoolCableCo-2.4G and CoolCableCo-5G as part of the default configuration suggested. (If you are fuzzy on what an SSID is, no worries: We will review that in this chapter.)
Inside the 2.4 GHz and 5 GHz bands, the radio frequencies are gathered into channels. In the 5 GHz band, there are no overlapping channels. This is wonderful, and it means that you do not have to worry about an AP using one channel interfering with a neighboring AP using an overlapping channel. Unfortunately, the 2.4 GHz band does include some overlapping channels.
To avoid problems when you are setting up a wireless access points in the 2.4 GHz band, you should be sure to use the nonoverlapping channels: 1, 6, and 11. Memorize these channels if you have not already.
Over the years, many IEEE 802.11 standards have emerged to take advantage of new wireless technology that operates in the 2.4 GHz and 5 GHz bands. Table 7.1 recaps them for you.
Table 7.1 IEEE 802.11 Wireless Standards
Standard |
Year |
2.4 GHz/5 GHz/Both |
Maximum Speed |
|---|---|---|---|
802.11 |
1997 |
2.4 GHz |
2 Mbps |
802.11b |
1999 |
2.4 GHz |
11 Mbps |
802.11a |
1999 |
5 GHz |
54 Mbps |
802.11g |
2003 |
2.4 GHz |
54 Mbps |
802.11n |
2009 |
Both |
600 Mbps |
802.11ac |
2013 |
5 GHz |
6.93 Gbps |
802.11ax |
2019 |
Both |
Up to 30% faster than 802.11ac |
A wireless device can support more than one of the standards shown in Table 7.1, but your device and wireless client must agree on and use a single standard as they communicate.
Each wireless network has a service set identifier (SSID), which is a string of characters used to uniquely identify that network. Most simply think of it as the wireless network name, and that certainly works.
In low-security environments—perhaps your home—the SSID is typically broadcast by the AP. You can fire up a computer, have the computer dynamically scan for available SSIDs, and then pick a wireless network to join.
More secured environments may not broadcast the SSID; this is known as network cloaking. Keep in mind that network cloaking does not increase the security of a wireless network. It does, however, mean that client devices must be configured with the precise name of the network as they will not be able to dynamically scan and find it.
ExamAlert
Eliminating the SSID broadcast is actually a small step in wireless security. Modern tools do not need to be very sophisticated to find the SSID that is being sent through the air in a certain location. For security, it’s important to use security measures, as discussed in Chapter 27, “Describe and Configure Wireless Security Protocols.”
CramQuiz
1. What 2009 Wi-Fi standard uses both the 2.4 and 5 GHz bands?
A. 802.11g
B. 802.11n
C. 802.11b
D. 802.11ac
2. How do you identify a wireless network?
A. Using the RF band and AP MAC combination
B. Using the IP address of the AP
C. Using the SSID
D. Using the passphrase
CramQuiz Answers
1. B is correct. 802.11n, which was released in 2009, features use of both the 2.4 GHz and 5 GHz bands.
2. C is correct. We typically locate and connect to a wireless network by using its name, technically known as the SSID.
Review Questions
1. What is a basic security measure used in some wireless networks?
A. Network cloaking
B. RF cloaking
C. SSID broadcasting
D. MAC masking
2. What wireless standard introduced in 2013 permits a maximum speed of 6.93 Gbps?
A. 802.11ax
B. 802.11g
C. 802.11ac
D. 802.11n
Answers to Review Questions
1. A is correct. A simple security measure that is sometimes used in combination with stronger measures is to prevent the broadcast of the SSID; this is known as network cloaking.
2. C is correct. 802.11ac, which was introduced in 2013, shattered previous maximum throughput limits. This technology uses the 5 GHz band and allows a maximum speed of 6.93 Gbps.
Additional Resource
WiFi Standards (and how they work)