Wireless Networking and the CCENT Exam

If you are preparing for the new Cisco CCENT exam, you’ve probably noticed that it requires you to have a fundamental understanding of wireless networking as it is used in a wireless local area network (WLAN). The key to understanding what you need to know for this part of the exam is the primary objective related to WLANs, which states: Explain and select the appropriate administrative tasks required for a WLAN.

Notice that you are not required to understand the modulation techniques in detail and you do not have to know the details of every Extensible Authentication protocol (EAP) type. You will need to be able to make good decisions based on an understanding of what these technologies offer, but you will not have to know the specific details of how they work.

The ultimate question becomes: What will you have to know? The answer is found by looking at the sub-objectives and relating them to the primary objective for WLAN knowledge. For example, the first sub-objective is to be able to describe standards associated with wireless media. Relating it to the primary objective it becomes: Explain and select appropriate administrative tasks based on an understanding of standards associated with wireless media.

In other words, you will need to be able to choose the right wireless standard for a given situation. Consider the following list of standards and their key characteristics as well as some traditional facts of WLAN technology:

     • IEEE 802.11g – 54 Mbps data rate, 2.4 GHz unlicensed band, 3 co-located APs
     • IEEE 802.11a – 54 Mbps data rate, 5 GHz unlicensed band, 8 co-located APs
     • IEEE 802.11b – 11 Mbps data rate, 2.4 GHz unlicensed band, 3 co-located APs
     • Between 50 and 70 percent of the data rate is available for real data throughput depending on the environment in which the WLAN operates
     • 5 GHz signals that are limited by FCC regulations are more difficult to detect at greater distances than 2.4 GHz signals

Based on these standards and the features they provide, you can make an effective administrative decision in a given situation. For example, if you need to provide 180 Mbps of throughput within a small confined area, you would need to implement IEEE 802.11a access points. This is because three overlapping IEEE 802.11g access points would only provide a data rate of 162 Mbps and 40-50 percent of that would be lost to management overhead. You could easily implement six IEEE 802.11a access points in the small area and accomplish a data rate of 324 Mbps. The throughput will most likely be between 190 Mbps and 230 Mbps for this IEEE 802.11a solution. Of course you would need to test in order to ensure that the environment does not introduce too much noise and thereby lower the actual throughput.

As you can see, you do not have to know that IEEE 802.11a uses Orthogonal Frequency Division Multiplexing (OFDM) or that IEEE 802.11g uses Extended Rate Physical OFDM in order to make this administrative decision. You will want to know the Physical Layer modulation used for the different standards, but the modulations do not factor into this decision directly. Even if you were presented with a question that asked what modulation scheme is used for a given standard, you would not need to know the low level details of how that modulation scheme works in order to answer the question.

The CCENT exam definitely tests your knowledge of networking technologies in small- and medium-sized businesses, but as you can see the knowledge required to pass the exam also helps you make excellent decisions in the real world. This makes the Cisco CCENT and CCNA exams that much more valuable.