Apply Your Knowledge
List the three encryption standards you can currently use with wireless networking.
Describe the differences between WEP, WPA, and WPA2. What type of encryption does each use? What are their strengths and weaknesses?
List three potential vulnerabilities of a wireless network.
Because a wireless access point forces all clients to use the speed of the slowest client, how do you think you should ideally deploy your wireless access points?
What is the process for successfully installing a wireless access point?
What is a rogue access point?
- ○ A. An unauthorized access point that has been placed on your LAN
- ○ B. An access point configured to broadcast the corporate SSID
- ○ C. An access point using WEP or WEP2 security
- ○ D. An access point that has been compromised by an intruder
When designing a wireless ESS system, how much cell overlap is recommended?
- ○ A. None. Cell overlap can cause interference.
- ○ B. 5 to 10%
- ○ C. 10 to 15%
- ○ D. 15 to 20%
What scenario would be an ideal case to implement WEP security?
- ○ A. You are running a small business network environment implementing the 802.11a wireless standard
- ○ B. You would like to implement the 802.1x security standard using a Windows RADIUS server to authenticate users
- ○ C. You would like to implement increased security instead of or in addition to the typical WPA or 802.11i standards
- ○ D. You are required to implement wireless using older equipment that does not support WPA or WPA2
You are sitting in a library and would like to share files with a coworker sitting across the table. To accomplish this, the coworker connects to a wireless SSID managed by your laptop. What type of network topology is this?
- ○ A. Unsecure
- ○ B. Ad hoc
- ○ C. Basic Service Set
- ○ D. Extended Service Set
You are using a Cisco 7921 wireless VoIP device. While speaking to your coworker on the phone, you are walking through multiple wireless cells. What type of network topology is this?
- ○ A. Unsecure
- ○ B. Ad hoc
- ○ C. Basic Service Set
- ○ D. Extended Service Set
Your organization uses a wireless security standard that requires people to authenticate to a back-end server with a valid active directory username and password before they are granted access to the wireless network. Upon successful authentication, the dynamic encryption keys are generated for use during the wireless session. What type of network security is in use?
- ○ A. WEP
- ○ B. WEP2
- ○ C. WPA
- ○ D. 802.11i
- ○ E. 802.1x (EAPOL)
Which of the following accurately describes the difference between WPA and WPA2?
- ○ A. WPA integrates with WEP encryption standards, whereas WPA2 is not backward-compatible.
- ○ B. WPA uses TKIP encryption, and WPA2 uses AES.
- ○ C. WPA uses preshared keys, and WPA2 allows for back-end user authentication.
- ○ D. WPA is used on 802.11a networks, whereas WPA2 is compatible with 802.11a/b/g networks.
You are troubleshooting a wireless laptop for a user in your organization. The wireless laptop cannot identify any available wireless SSIDs in the region. Your personal laptop can identify three SSIDs from the same location. The user has previously connected to the corporate network without issue. You have noticed increased interference from a neighboring company during different times of the day. What is the most likely cause of this issue?
- ○ A. The client wireless network card is disabled.
- ○ B. The RF interference has become too heavy for the client to view the available SSIDs.
- ○ C. The client wireless card is using the wrong frequency.
- ○ D. The signal is being absorbed before reaching the client laptop.
You suspect that one of your network users has violated the corporate security policy by plugging in a personal wireless access point in his cubicle. What Cisco security solution would allow you to detect this issue?
- ○ A. Cisco ACS Server
- ○ B. Cisco wireless IPS
- ○ C. Cisco wireless 802.1x
- ○ D. MAC address security
A network user has issued a trouble ticket stating that she is experiencing file transfers well below the 54Mbps speed that her wireless laptop claims to achieve. What are three valid reasons for this?
- ○ A. RF interference
- ○ B. CSMA/CA transmission method
- ○ C. Proximity to the access point
- ○ D. The duplex setting on the client's laptop
- ○ E. The client has not implemented 802.1x
Answers to Review Questions
The three encryption standards are WEP, WPA, and WPA2.
WEP uses the RC4 encryption algorithm. WPA uses the TKIP encryption method, which is more secure than WEP but not as secure as the WPA2 standard, which uses AES encryption. WEP does not have many strengths other than compatibility; all wireless devices can support the WEP standard. WPA has the strength of being interoperable with older WEP-compatible hardware, but it still has a few security weaknesses. WPA2 supports extremely strong encryption, but it is not backward-compatible with older wireless hardware.
Wireless networks are vulnerable to war driving, direct hacking, and employee ignorance.
Wireless access points should be deployed in a "tight configuration." This means that you should have many access points broadcasting smaller, more high-speed signals rather than a few access points broadcasting weaker signals that reach a larger radius.
First, ensure hardwire operation. Then, install the access point and test a basic network SSID with no security. Finally, add security and perform a final test.
Answers to Exam Questions
A. Rogue access points typically are brought in by internal corporate users with nonmalicious or malicious intent. Regardless of the intent, the rogue access point adds an enormous security liability to your network.
C. Wireless best practices recommend a 10 to 15% overlap of wireless cells. This allows for seamless roaming by wireless devices. Answer A is true only if the wireless access points are configured to use the same channel (frequency range). Because of this, you should never have adjacent access points using the same channel.
D. Both WEP (64-bit) and WEP2 (128-bit) encryption methods have been found to be insecure. The only time they should be used is in a network environment that uses older equipment and is unable to support the newer security standards.
B. Ad hoc networks are wireless networks generated from a participating device in the network, such as a laptop. These laptops can use many of the same security methods as BSS or ESS wireless topologies.
D. An Extended Service Set (ESS) wireless topology is the combination of two or more Basic Service Set (BSS) networks. This allows client roaming (between wireless cells) without service interruption.
E. 802.1x (less commonly known as Extensible Authentication Protocol over LAN [EAPOL]) adds a secure authentication system to a LAN environment. This technology can be used to secure both wired and wireless LAN connections. The other answers represent varying encryption standards.
B. WPA was released as an interim solution to improve the security of WEP. It uses an encryption method known as TKIP, which is more secure than WEP but not as secure as the WPA2 standard, which uses AES encryption.
A. The most likely cause of this issue is that the client wireless card is turned off. This happens frequently with laptops, because manufacturers commonly put a switch or button on the case of the laptop that easily turns the laptop on or off. The fact that it could not see any wireless networks while your personal laptop sat next to it reveals that wireless networks are reaching the location through the interference. The card cannot be the wrong frequency, because it previously connected to the corporate network without issue.
B. The Cisco wireless IPS system identifies rogue wireless access points added to the network. The 802.1x and the Cisco ACS Server are primarily responsible for user authentication and privileges. MAC address security can help disable a port with a rogue wireless access point, but it cannot detect the rogue's existence.
A, B, C. Wireless is susceptible to many types of RF interference. Likewise, the farther the client is from the access point, the lower her speed becomes. Finally, wireless uses a CSMA/CA transmission method, which causes the amount of bandwidth to diminish the more clients you add to the access point.
Suggested Readings and Resources
- Wikipedia 802.11 definitions, http://en.wikipedia.org/wiki/802.11
- How WiFi Works, http://computer.howstuffworks.com/wireless-network3.htm
- Chris Ward and Jeremy Cioara. CCNA Practice Questions. Que Publishing, 2008.
- Toby Velte and Anthony Velte. Cisco 802.11 Wireless Networking Quick Reference. Cisco Press, 2005.