13. A wireless LAN is being deployed inside the new one room office that is occupied by the park ranger. The office is located at the highest part of the national park. After network testing is complete, the technicians report that the wireless LAN signal is occasionally affected by some type of interference. What are two possible causes of the signal distortion? (Choose two.)
- the microwave oven
- the large number of trees that surround the office
- the cellular phones that are used by the employees
- the elevated location where the wireless LAN was installed
- the number of wireless devices that are used in the wireless LAN
Explanation: Wireless LAN connectivity is not affected by trees or the elevation of the equipment. Because this is a one room office in an isolated area, there will not be a large number of wireless devices or source of interference operating in the immediate vicinity, apart from a cellular phone or a microwave oven.
14. Which protocol could be used by a company to monitor devices such as a wireless LAN controller (WLC)?
- NTP
- PAT
- SNMP
- SSH
Explanation: The Simple Network Management Protocol (SNMP) is an application layer protocol used to monitor and manage the network. Network devices must be configured with a community name and IP address of the SNMP server.
15. HealthOne, Inc. provides wireless connectivity in its clinic facilities for staff access to internal network resources. The wireless security policy specifies that the staff must perform user-based authentication with a special back-end authentication server before they are allowed to access the WLAN. Which technology should be chosen in the WLAN implementation to meet this requirement?
- EAP
- PSK
- WEP
- WPA
Explanation: Extensible Authentication Protocol (EAP) is an authentication framework that supports multiple authentication mechanisms without having to pre-negotiate a particular one. EAP authentication is initiated by the server (authenticator), whereas many other authentication protocols are initiated by the client (peer).
16. A threat actor uses network scanning tools and penetration tools to discover the IP address and manufacturer of a home wireless router. The threat actor then uses internet searches to discover the default administrative access details. Successful remote access of the home router allows the threat actor to use it as a vector to attack other devices. Which element of smart home security is affected by this attack?
- WPA2
- firmware
- encryption
- authentication
Explanation: In general, the security requirements for a Smart Home should include these:
- WPA2 – The wireless network should use the latest Wi-Fi security which is currently WPA2.
- Encryption – It protects the confidentiality and integrity of information transmitted over a network.
- Authentication – Strong authentication protects the device from unauthorized use or reconfiguration and prevents disclosure or modification of the data stored on the device.
- Firmware – The IoT device manufacturers should update the firmware for any newly discovered vulnerabilities. The home IoT device users should enable the checking of updates automatically.
17. Which device provides wireless connectivity to users as its primary function?
- switch
- router
- access point
- modem
Explanation: A switch connects multiple devices to a network. A router will forward traffic between networks. A wireless router will connect multiple wireless devices to a network. An access point will provides wireless connectivity to multiple devices and has fewer features than a wireless router. A modem will connect a home or small office to the Internet.
18. What is a DHCP scope as it relates to a WLAN configured on the WLC controller?
- a corporate plan for allocation of IP addresses for wireless clients
- a pool of IP addresses for WLAN clients
- security rules associated with DHCP for WLANs
- the distance allotted for wireless clients that can receive IP addressing information
Explanation: When configuring a WLC controller as a DHCP server, use the DHCP Scope menu option to configure IP address-related settings such as the range of IP addresses to assign to WLAN devices, a DNS server address, and lease time.
19. Included in a Bill of Materials (BOM) for a SOHO wired implementation is a Cisco 2811 router, Catalyst 2560 switch, four PCs, three laptops, and a networked printer. Wireless LAN capability will be implemented on this network. Which two equipment types must be added to the BOM to implement this request? (Choose two.)
- DNS server
- LAN switch
- wireless NICs
- DHCP server
- wireless access points
Explanation: In order to connect to a 802.11 WLAN network, a client must first authenticate and then associate with the AP. Because association only occurs on wireless infrastructure networks, wireless NICs and at least one AP (access point) would be required by the clients.
20. Which WLC tab would a network administrator typically use to see a summary view of the most heavily used WLANs including the number of clients using a particular WLAN?
- Commands
- Controller
- Monitor
- WLANs
Explanation: Use the Monitor tab and then the Summary option to see information about the WLC, including the IP address and system uptime as well as information associated with the top WLANs configured and active within the organization.
21. A network administrator is configuring the SNMP function on a Cisco 3500 series WLC. The task is to add an SNMP trap server to which this WLC will forward SNMP log messages. Which tab should the administrator use to add the SNMP trap server information?
- MONITOR
- COMMANDS
- CONTROLLER
- MANAGEMENT
Explanation: On the Cisco 3500 series WLC, click the MANAGEMENT tab. SNMP is listed at the top of the menu on the left. Click SNMP to expand the sub-menus, and then click Trap Receivers. Click New… to configure a new SNMP trap receiver.
22. After the administrator manually configures the correct SSID on a new laptop, the computer is still unable to connect to the wireless LAN. Which additional action should the administrator take to resolve this problem?
- Modify the group account of the user to include all file permissions.
- Reboot the wireless access point.
- Rename the laptop and reset the user password on the network.
- Verify that the MAC address for the laptop is in the MAC address filter table.
Explanation: MAC address filtering sets up authorized MAC addresses, preventing unauthorized devices from accessing the WLAN. When adding a new device to a WLAN with a MAC filter, the MAC address of the new device must be added to the filter list before it will be able to join the network.
23. Which feature or function does an AP provide in a wireless LAN?
- An AP is easier to configure and to set up than Wi-Fi range extenders.
- Each AP advertises one or more SSIDs and a user can choose to connect to the closest SSID.
- A wireless device has to be associated to an AP in order to have access to network resources.
- A wireless client can connect to more than one AP at a time.
Explanation: Although range extenders are easy to set up and configure, the best solution would be to install another wireless access point to provide dedicated wireless access to the user devices. Wireless clients use their wireless NIC to discover nearby APs advertising their SSID. Clients then attempt to associate and authenticate with an AP. After being authenticated, wireless users have access to network resources.
24. Which statement describes an autonomous access point?
- It is used for networks that require a large number of access points.
- It is a standalone access point.
- It is server-dependent.
- It is managed by a WLAN controller.
Explanation: An autonomous access point is used in environments that require a small number of access points. As network demands increase, more access points can be added to the environment with each access point acting independently of another. An autonomous access point can be configured using either a GUI or CLI.
“Do I Know This Already?” Quiz Answers:
1. Which of the following is considered to be the best first step in troubleshooting a wireless problem?
- Reboot the wireless LAN controller
- Gather more information to find the scope of the problem
- Access the WLC and search for clients in the error logs
- Access the WLC and look for alarms; if none are found, close the incident ticket
Explanation: The first course of action should always be to gather as much information as possible so that you can reduce the scope of the problem. Then you can investigate the few potential causes that remain.
2. To troubleshoot a single wireless client, which one of the following bits of information would be most helpful in finding the client device in a wireless LAN controller?
- The Ethernet MAC address of the client device
- The end user’s name
- The wireless MAC address of the client device
- The name of the application having issues
Explanation: The wireless MAC address is always an important parameter because you can enter it into the search bar of a WLC to find the client device.
3. Suppose you have accessed a WLC to search for a client’s MAC address. Information about the client is displayed, along with a sequence of dots indicating connectivity. The last green dot in the sequence is labeled Online. Which one of the following statements is the most correct?
- The client device is powered up and online but has not begun to join the wireless network.
- The client device has successfully joined the wireless network.
- The client device has associated with an AP to get online but has not authenticated successfully.
- None of the above
Explanation: The status Online means that the client has passed through each phase and policy that the WLC required and has successfully joined the wireless network.
4. According to the Connectivity chart on the WLC’s Client View screen, which one of the following states indicates that a wireless client has met all of the requirements to begin using a wireless network?
- Association
- Start
- Authentication
- DHCP
- Online
Explanation: The status Online means that the client has successfully joined the network. The other states occur earlier in the connection sequence.
5. Suppose an end user tried to join a wireless network several minutes ago. The WLC Client View screen shows the client to be in the Association state but not the Authentication state. Which one of the following best describes the client’s current condition?
- The client does not support any of the 802.11 amendments.
- The client has an incorrect pre-shared key.
- Spanning Tree Protocol is blocking the AP’s uplink.
- The client failed to receive an IP address.
Explanation: The client has not yet passed the Authentication stage, so it must have failed to authenticate itself correctly. If the WLAN uses WPA2-Personal, then the client’s pre-shared key could be incorrect.
6. Suppose that you have a large wireless network with several controllers, many APs, a RADIUS server, and a syslog server. A user has reported connectivity problems in a specific building location but has provided no details about the AP or controller he tried to join. Which one of the following is the most efficient troubleshooting method you can use to find information about the client?
- Go to the client’s location and use your own computer to associate with the network and then find out which AP and controller you are using
- Access each WLC and check the status of every AP that is joined to it
- Search for the client’s MAC address on each controller
- Search for the client’s MAC address on the RADIUS server
Explanation: Out of the possible answers, the most efficient method would be to access each controller and search for the user’s MAC address. That would give you important information specific to that user. You could also leverage Prime Infrastructure or DNA Center to search for the client across all managed controllers at once. If you choose to use your own computer, you may never be able to duplicate the conditions the user had when he experienced the problem. Checking each AP is not an efficient approach because you have not narrowed the scope of the problem. Checking the RADIUS server might reveal some authentication problems, but only if the user’s problem involved failed authentication.
7. Suppose you search a WLC for a client device’s MAC address. The results show a Connection Score value of 10%. Which one of the following correctly describes the scenario?
- The client is using its connection only 10% of the time.
- The client is currently in the bottom 10% of all wireless clients in data usage.
- The client has a received signal strength of 10% at the AP.
- The client is currently using a data rate that is 10% of its maximum capability.
Explanation: The Connection Score indicates the client’s actual data rate as a percentage of its maximum supported data rate, assuming that the AP’s maximum data rate is higher.
8. Suppose that you have just received news that no users can connect with a newly installed AP. Which one of the following bits of information would be important when you search for the AP’s name from the WLC? (Choose all that apply.)
- The AP has a valid IP address.
- The AP is not found.
- The AP has no channel numbers listed for the 2.4 and 5 GHz bands.
- The AP has a valid MAC address.
Explanation: The first three choices are important facts in troubleshooting the connectivity issues. For example, if you see a valid IP address listed for the AP, then it must be properly connected to the wired network, have appropriate power, and have discovered and joined the WLC. As a result, you can probably rule out wired connectivity problems at the AP. If the AP is not found in the WLC search, then the AP might not be powered on, might not have an IP address, or might not have discovered the WLC. Therefore, users would not be able to use the AP at all. If the AP has no channel numbers shown, then perhaps the wireless bands have not been enabled on the WLC, so the users have no BSS to discover and join. Knowing that the AP has a valid MAC address probably has no relevance at all because all APs are preconfigured with valid MAC addresses at the factory.
9. Suppose you search for an AP on a WLC and notice that Noise is −20 on the 2.4 GHz band. Which of the following statements is correct?
- The noise is at a very low level, which is good for wireless performance.
- The noise is at a very high level, which is good for wireless performance.
- The noise is at a very low level, which is bad for wireless performance.
- The noise is at a very high level, which is bad for wireless performance.
Explanation: The noise level is measured in dBm, from 0 dBm to −100 dBm or more. For the best wireless performance, you want the noise level to be as minimal as possible, so −100 would be best. Because the actual level is −20, performance is probably very bad around the AP.
10. Suppose you access a WLC and search for the name of a specific AP for which users have complained about problems. When you look at the 5 GHz information about the AP, you notice that it is using channel 60 and has 5 dBm transmit power, 65 clients, −90 noise level, 1% channel utilization, and the Air Quality value 10. Which of the following conclusions would be most accurate?
- The AP has too many clients using the 5 GHz channel, which is causing poor performance.
- The noise level is too low, which is causing poor performance.
- The channel utilization is too low, which is keeping clients from using the channel.
- The Air Quality value indicates a severe problem with interference on the channel.
Explanation: The Air Quality level of 10 is very low, considering that 100 is the highest and best value. Therefore, something must be interfering with the AP and client operation on that channel. It might be tempting to see the large number of clients on the AP and assume that there are too many to share the same channel. However, the channel utilization is very low, indicating that the 65 clients are mostly idle or quiet, leaving plenty of air time available for use. Likewise, a noise level of −90 dBm is very low and does not indicate a problem.