EMT Practice Test

1. Question Content...

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Question1: You are considering disabling the data rates of 1, 2, 5.5 and 11 in the 2.4 GHz band.
What advantage might this provide to the networks operating in this band?

Question2: You are responsible for troubleshooting and analysis of the WLAN in your organization that supports more than 700 client STAs. Forty APs are deployed and they are all dual-band APs and are controller-based.
You must troubleshoot the wired side in some scenarios using a protocol analyzer.
Which one of the following problems would warrant wired-side analysis in most situations?

Question3: What is the formula used to calculate the Duration field value in an RTS frame?

Question4: You are using a laptop-based protocol analyzer to scan all channels and determine the basic configuration of the WLAN Basic Service Set in your facility. You are scanning all channels. All configured with default settings.
What can you change to cause the scan to run faster while still APs are capturing beacon frames on all the channels?

Question5: While troubleshooting DHCP issues, you perform a protocol capture in order to determine if the DNCP pool is depleted. The capture does not show DHCPnak messages.
Where else could you look to determine if the pool is depleted?

Question6: You are troubleshooting VoIP WLAN issues. When performing a PING to a remote device that would be involved in a call link, you see that the time value averages 220 milliseconds.
How much extra delay beyond that recommend for VoIP links is in this link?

Question7: What is the Extended IFS used in 802.11 contention?

Question8: You need to determine RF activity over time in a spectrum analyzer. It is to be able to see the activity and the amplitude of that activity.
What kind of view should be used?

Question9: You are working in an organization that has implemented an SCA-based WLAN. You want to change the RF channel for a single AP.
What can you do to perform this task with some SCA solutions?

Question10: You require 802.11ac capture solution. You want to capture using native operating system tools if possible.
What operating system has built-in ability to capture 802.11ac frames assuming it is running on the appropriate laptop hardware?

Question11: You are evaluating a protocol capture file in Wireshark. The following filter is applied:
wlan_radio.11ac.bandwidth - - 4
What kind of frames are displayed?

Question12: You are using the real-time FFT display of a spectrum analyzer.
In what domain does this show the RF energy detected in the swept frequencies?

Question13: You are creating a baseline configuration for a pool of 100 laptops related to Wi-Fi. The laptops have dual- band 802.11ac adapters. They are configured for aggressive roaming.
What additional setting might you configure to ensure they access the WLAN on the channels with the least interference assuming the enterprise WLAN is well-designed?

Question14: ABC Company requires the ability to identify and quickly locate rogue devices. ABC has chosen an overlay WIPS solution with Wi-Fi sensors that use dipole antennas to perform this task. No other sensors are included. Use your knowledge of location tracking techniques to answer the question.
Which one of the following location methods is not available in the described system?

Question15: You are explaining capacity planning to another engineer assisting you on a WLAN implementation project.
As part of the explanation, you provide the following formula: C = B * log2(1 + S/N).
What does this formula define?

Question16: When evaluating modulation and coding schemes, you must determine the best coding rate available. In
802.11 MCS tables, what is the best coding rate from the perspective of highest data rates?

Question17: Given: Adjacent Channel Interference (ACI) can cause frame corruption and poor performance in WLANs.
You are using a protocol analyzer in the attempt to detect ACI.
What should you look for in such a scenario?

Question18: You have been asked to recommend a protocol analysis solution that uses open source software and works with the Linux platform. It must provide decoding of 802.11ac frames and minimal support for reporting and statistics.
What solution would you recommend?

Question19: The data rate for a data frame is 150 Mbps in 5 GHz.
What rate is used to transmit the PHY header information?

Question20: You are analyzing a problem with a specific client adapter. The vendor specifications sheet does not provide detailed information.
What tool can you use to provide the most detailed specification information in many such cases?

Question21: You work as an SE for a value-added reseller. A client has an existing deployment of 802.11n Aps and wants to upgrade several BSSs to 802.11ac.
What hardware feature of some enterprise Aps may allow for this without a forklift upgrade?

Question22: You are using a Wireless Aggregator utility to combine multiple packet captures. One capture exists for each of channels 1, 6 and 11.
What kind of troubleshooting are you likely performing with such a tool?

Question23: When using Wireshark for protocol analysis, what filter will allow you to see only beacon frames?

Question24: Several users have reported WLAN network connection issues and the users connect to the same AP.
These users are spread throughout a 320 square meter area. Using a spectrum analyzer, you see RF energy across the entire 2.4 GHz band at significant signal strength levels. The users all connect using either HT or ERP devices.
What is the likely cause of this problem within this area?

Question25: You have received reports of performance problems in a BSS. One specific user is indicating that her downloads are taking a very long time compared to other users around her. You want to determine if the AP is sending frames multiple times to get through to the user's computer.
Where should you monitor with the protocol analyzer to see retries from the AP in this scenario?

Question26: You have implemented centralized, infrastructure-based spectrum analysis. The Aps are configured to perform spectrum analysis in an ad-hoc manner and will go offline as Aps to perform this duty when needed.
What unique method of spectrum analysis monitoring is provided by this solution that is not typically available in a laptop-based analyzer?

Question27: You want to simplify viewing frames of a particular type in Wireshark.
What is used to specify frames for colorization?

Question28: You are considering the performance of a BSS based on different PHY types used. In the BSS, one device must use ERP as it does not support HT in its 2.4 GHz band.
What is the duration of the interframe space for this ERP device for standard data frame transmissions?

Question29: You are troubleshooting problems with DHCP in relation to lightweight APs. They vendor class identifier (VCI) is not specified in the DHCP server. When you contact vendor support, they inform you that it is not necessary.
When is this information true?

Question30: You have captured 802.11 traffic using an adapter that includes the radio tap header. You see several frames often called announcement frames in the capture.
What best describes these types of frames?

Question31: You suspect an interfere may exist in a BSS that is experiencing sporadic problems. You want to identify and locate the device. The actual device identify is not known.
What tool should be used for this purpose?

Question32: The To DS bit is set to 0 and the From DS is set to 1.
What best describes this 802.11 frame?

Question33: You have been recently hired as the wireless network administrator for an organization spread across seven locations. They have deployed more than 100 APs, but they have not been managed in either an automated or manual process for more than 18 months.
Given this length of time, what is one of the first things you should evaluate from a support perspective?

Question34: You are attempting to determine timing information within a packet capture of a WLAN protocol analyzer.
What time is used to display the time the packet was captured based on the system clock in the computer?

Question35: VoIP is used heavily in your organization. You must troubleshoot problems with dropped calls on the WLAN.
What is a common cause of dropped calls when using Wi-Fi VoIP phones?

Question36: A manager at a retail outlet has complained that an incident occurred allowing a STA to launch an attack against another STA connected to their public Wi-Fi hotspot. He has asked you to troubleshoot the situation and verify that all possible measured are being taken to prevent this.
What configuration should you check in the AP?

Question37: You are performing 802.3 network analysis. For what are the DA and SA fields used in the frame header?

Question38: The manager in the security group is concerned about compliance with security policies on the WLAN. The budget is not available for a full WIPS SOLUTION. He has asked you to implement a process that will verify compliance.
What would you recommend in such a scenario?

Question39: You must report on frame types seen on the WLAN. You want to list the frame types by both name and binary value.
What frame type is represented by the binary value 011010, which includes the Type and Subtype values?

Question40: You have been asked to recommend a solution for protocol capture of 802.11 frames consisting of 3x3:3
802.11ac communications. The requirement specifies that you gain a general view of a coverage area and does not require that you capture from specific user locations. The solution must be the least expensive practical solution possible that does not disrupt user access to the WLAN and it must be based on enterprise WLAN hardware.
What solution would you recommend so that any coverage area could be monitored on demand?

Question41: To what data rates can a 5 GHz PHY device shift when changers occur in the signal strength?

Question42: What element was added to the general frame of 802.11 with the 802.11e amendment and the 802.11-
2007 rollup?

Question43: You are concerned about attackers gaining access to your WLAN from outside the facility.
Why does reducing the output power on the APs not provide sufficient certainty that an attacker outside the facility cannot gain access?

Question44: You are troubleshooting throughput problems for a WLAN cell. The cell is provisioned with an 802.11ac dual-band AP. Users connected with both 5 GHz and 2.4 GHz connections are reporting performance problems. The AP settings are properly optimized. No interface issues have been detected (either co- channel interference or non-Wi-Fi interference) and the number of associated users is low.
What should you analyze to resolve the issue?

Question45: When using a commercial WLAN protocol analyzer, you notice that it is listing vendor names for some APs and client STAs.
What is the source of this information?

Question46: You are tasked with describing the various frames used in 802.11 communications.
What frame is used for spectrum management, fast BSS transition and some other actions taken within a BSA?

Question47: You view a protocol analyzer capture decode with the following protocol frames listed in the following order (excluding the ACK frames): 1) 802.11 Probe Request and 802.11 Probe Response 2) 802.11 Auth and another 802.11 Auth 2) 802.11 Assoc Req and 802.11 Assoc Rsp 4) EAPOL-Start 5) EAP Request and EAP Response 6) EAP Request and EAP Response 7) EAP Request and EAP Response 8) EAP Request and EAP Response 9) EAP Request and EAP Response 10) EAP Success 19) EAPOL-Key (4 frames in a row)
What are you seeing in the capture file?

Question48: During an initial install of a controller-based WLAN, the APs are not locating the WLAN controller. The controller is two router hops away from the nearest AP. DHCP is not used. When performing a packet trace, you see a DNS response code of 3 targeted at one of the APs.
What is the problem?

Question49: What action is taken automatically by 802.11 APs and client STAs as the signal strength of the link weakens in order to improve the quality of the RF communications overall?

Question50: Recently, three rogue APs have been connected to the network and later discovered. You want to prevent future rogue AP installations as much as possible.
What is the first step to eliminating or reducing rogue APs on the network?

Question51: Given: Protocol analyzer often have useful graphical dashboards providing information about the health and operations of the WLAN.
What is a valid use of a graph showing the Top APs Based on Active Associations?

Question52: You are attempting to work through a user complaint with the CWNP-recommended troubleshooting methodology.
What must be clearly identified in order to reduce the number of possible causes at step three?

Question53: A new firmware has been released for the AP model you use in your WLAN. You have more than 120 of these APs installed.
What is a good reason for applying a firmware update on an enterprise AP?

Question54: You are troubleshooting a connection problem with a client STA. Regardless of the AP to which it attempts to connect, the connection fails. Using a wired protocol analyzer, you determine that the problem is with the 802.1X/EAP authentication to the RADIUS server.
What layer or range of layers of the OSI model revealed this information?

Question55: As the WLAN administrator in your organization you are responsible for troubleshooting connection issues.
Several STAs are connecting to the network, but are unable to communicate after connection. You suspect a DHCP problem. After capturing traffic on the wired-side of the AP, you want to view only DHCP traffic.
What filter in Wireshark can be used for this purpose?

Question56: As the WLAN engineer in your organization, you must troubleshoot performance problems related to co- channel interference (CCI).
What is a good measurement of CCI impact in addition to the number of APs seen on a channel?

Question57: You have implemented an AP at a remote office. It is a single-band AP supporting 802.11ac. Several users complain that their laptops cannot connect to the WLAN. These laptops are from multiple vendors and range in age from 2 to 4 years. The SSID and security profile settings are correct. All default settings were used on the AP with the exception of the SSID and security settings.
What is the most likely issue preventing these STAs from connecting to the AP?

Question58: iPerf is a tool used in what category of testing?

Question59: You are repairing a misconfiguration in WMM settings on an AP. The aCWmin and aCWmax values were all changed.
What is the default aCWmax for AC_BK?

Question60: You are concerned with management overhead in your WLAN. When evaluating the network, you note that each dual-band AP provides for 4 SSIDs in each band with three secure SSIDs and one Open System SSID. The network runs only 802.11ac APs and uses 20 MHz channels in 2.4 GHz and 400 MHz channels in 5 GHz.
What can you do to reduce the impact of beacon frames on CCI and channel utilization?