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Exam A QUESTION 1
Which of the following markers can be set by Committed Access Rate (CAR)? (Choose all that apply.)
A. DSCP bits
B. QoS Group
C. ATM CLP bit
D. Frame Relay DE bit
E. IP precedence bits

Correct Answer: ABE Section: (none) Explanation
Explanation/Reference:
Explanation:

Source: Cisco IP QoS Introduction, Page 64

QUESTION 2
What makes the DiffServ model more scalable than the IntServ model? (Choose all that apply.)
A. DiffServ makes use of per-aggregate QoS instead of per-flow QoS.
B. DiffServ makes use of hop-by-hop signaling which allows DiffServ to scale to a larger number of application flows.
C. DiffServ is capable of implementing admission control either locally on the routers or be offloaded to a central policy server using the COPS protocol.
D. DiffServ routers are not compelled to track the state information for each individual flow.
Correct Answer: AD Section: (none) Explanation
Explanation/Reference:
Incorrect:
B. No hop-by-hop signaling uses per-hop behavior
C. This is a feature of both models Sources: Cisco IP QoS Introduction http://www.cisco.com/en/US/tech/ CK5 43/ CK7 66/technologies_white_paper09186a00800a3e2f.shtml
QUESTION 3
The newly appointed Certkiller trainee technician wants to know what the benefits of using traffic shaping to implement network rate limiting is.What will your reply be? (Choose all that apply.)
A. Traffic shaping is an effective tool for rate-limiting VoIP traffic.
B. It will not increase packet loss.
C. It will not add to packet transit delays.
D. Traffic shaping can interact with congestion mechanisms embedded in Frame Relay.
E. Traffic shaping can be used on inbound and outbound traffic on a router.
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Incorrect:
A. Shaping adds variable delay to traffic, possibly causing jitter C. A shaper typically delays excess traffic using a buffer E. This is a feature of policing
Explanation: Source: Cisco IP QoS Traffic Shaping and Policing

QUESTION 4
Study the Exhibit below carefully: Router# show interfaces hssi 0/0/0 rate-limit Hssi0/0/0 45Mbps to R1 Input matches: all traffic params: 20000000 bps, 24000 limit, 24000 extended limit conformed 8 packets, 428 bytes; action: transmit exceed 0 packets, 0 bytes; action: drop last packet: 8680ms ago, current burst: 0 bytes last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps Output matches: all traffic params: 20000000 bps, 24000 limit, 24000 extended limit conformed 0 packets, 0 bytes; action: transmit exceed 0 packets, 0 bytes; action; drop last packet: 8680ms ago, current burst: 0 bytes last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps According to the exhibit, the router has been configured with Committed Access Rate (CAR) to rate limit traffic. What data rate has the traffic been limited to?
A. 192 Kbps
B. 2400 Kbps
C. 4,5 Mbps
D. 20 Mbps
E. 40 Mbps
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:

In the configuration example, CAR is applied on the input and output of a customer interface on the provider edge router. Traffic is policed to 256 Kbps on input and output, with some bursting allowed. All exceeding traffic is dropped at the provider edge. The result of the configuration is that traffic to and from the customer is limited to the average rate of approximately 256kbps (256000 in the configuration) with sustained bursts of approximately 32kbps (4kBps or 4000 in the configuration). Initial bursts at line speed can last up to 3 seconds because the token bucket can hold up to 96000 tokens (bytes) which equals 768000 bits (3 x 256000 bits). Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-91
QUESTION 5
The newly appointed Certkiller trainee technician wants to know which type of software queuing mechanism is Frame Relay Traffic Shaping implemented with on the physical interface. What will your reply be?
A. Priority Queuing (PQ)
B. Custom Queuing (CQ)
C. FIFO
D. Weighted Fair Queuing (WFQ)
E. IP Real Time Transport Protocol (RTP) Priority
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation: Works on any (sub) interface type Shapes traffic on that (sub)interface basis Can use any physical interface queuing (FIFO, PQ, CQ or WFQ) Only uses WFQ as the shaping queue (that is, on the input of the shaper) In contrast, Frame Relay Traffic Shaping: Works only on Frame Relay (sub) interfaces Shapes traffic inside individual FR Virtual Circuits Only permits WFQ as the physical interface queuing method Can use any queuing method as the shaping queue (that is, on the input of the shaper) Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-47

QUESTION 6
Why is it beneficial to make use of Enhanced LMI (ELMI) on Cisco networks?
A. ELMI is responsible for providing virtual provisioning tools at the edge of the Frame Relay network.
B. ELMI permits routers to dynamically download QoS information from Cisco switches for use in traffic shaping or for congestion management purposes.
C. ELMI provides the router the ability to use additional QoS tools including rate limiting with CAR and the Modular QoS Command Line Interface (MQC).
D. ELMI allows the router to deliver packets at the line rate of the Frame Relay interface, regardless of the condition of the Frame Relay network.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation: Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-58

QUESTION 7
Which of the following statements are true when you compare DSCP and IP Precedence to each other? (Choose all that apply.)
A. DSCP is backwards compatible with IP Precedence.
B. DSCP cannot be easily mapped into QoS because of its expanded classification options.
C. DSCP is more granular the IP Precedence, since more marking combinations are available.
D. DSCP appears stubby when compared IP Precedence, since devices make use of DSCP as defined in RFC exclusively.
E. DSCP is 6 bits long and IP Precedence is 3 bits long.
F. DSCP is more restrictive than IP Precedence, since devices are only allowed to use DSCP as defined in RFCs.
Correct Answer: ACE Section: (none) Explanation
Explanation/Reference:
Explanation: A)DSCP is backward compatible with IP Precedence (Class Selector Code point, RFC 1812) but not with the ToS byte definition from RFC 791 (“DTR” bits) Reference: Introduction to IP QoS (Course) p.45
QUESTION 8
Which MQC command would you use to perform marking properly?
A. precedence 5
B. ip precedence 5
C. set ip precedence 5
D. set ip mark precedence 5
E. mark ip precedence 5
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: IP precedence is encoded into the three high-order bits of the ToS field in the IP header. It supports eight classes of which two are reserved and should not be used for user-defined classes (IP precedence 6 and 7). IP precedence 0 is the default value and is usually used for the best-effort class. The set ip precedence command marks packets of a class with the specified precedence value. Reference: Introduction to IP QoS (Course) p.9-104
QUESTION 9
Which of the following statements aptly describes a network well designed for QoS?
A. Packets are classified at each router, based on as many detail as possible, typically using extended IP ACLs to match the packets for classification.
B. Packets are classified at each router, based on socket address only, typically using extended IP ACLs to match the packets for classification.
C. Packets are classified and marked, close to the edge of the network. The packets are treated differently based on this marking at the routers in the middle of the network.
D. Packets are classified based on different parameters, but close to the edge of the network. The packets are automatically characterized based on flow at the routers.
E. Packets are classified based on socket address, at the router closest to the source of the traffic. The packets are automatically characterized based on flow at the routers.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: To achieve the same level of quality in both directions the packets going to and coming from the customer network must first be classified and marked. Classification and marking packets going to the customer network is a more difficult task because: 1) Classifying and marking must be performed on all edge routers. 2) Classifying and marking requires the identification of the customer network. Using PBR, CAR, CB-Policing or CB-Marking does not scale because it involves the use of access lists (this is especially difficult if customer networks are dynamically learned via BGP). Reference: Introduction to IP QoS (Course) p.2-35
QUESTION 10
The newly appointed Certkiller trainee technician wants to know which bit in the ATM header can be marked by the Class Based Marker to extend IP QoS policy into an ATM network. What will your reply be?
A. DE
B. PTI
C. FECN
D. CLP
E. BECN
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation: The ATM CLP Setting feature somewhat allows users to extend their IP QoS policies into an ATM network by setting the ATM CLP bit in ATM cells based on the IP Precedence value of the packets being sent. As congestion occurs in the ATM network, cells with the CLP bit set are more likely to be dropped, resulting in improved network performance for high priority traffic and applications. The set atm-clp command marks packets of a class with the ATM CLP bit as a part of an input or output policy. Source: Cisco IP QoS Modular QoS CLI Service Policy, Page 9-110

QUESTION 11
How many possible meaningful values are defined in the DSCP in a Differentiated Services environment?
A. 3
B. 8
C. 16
D. 32
E. 64
F. 128
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Explanation:
DSCP supports more classes (64) than IP precedence (8)
Reference: Introduction to IP QoS (Course) p.36

QUESTION 12
Which of the following features will allow the marking of packets according to the Cisco QoS Framework? (Choose all that apply.)
A. MQC
B. CQ
C. PQ
D. CAR
E. WRED
Correct Answer: AD Section: (none) Explanation
Explanation/Reference:
Explanation: The Modular Quality of Service Command Line Interface (MQC) was introduced to allow any supported classification to be used with any QoS mechanism. Some mechanisms have the capability to mark packets based on classification and/or metering (e.g. CAR, class-based marking, etc.) Reference: Introduction to IP QoS (Course) p.61
QUESTION 13
Which of the following can be classified as Call Admission Control methods? (Choose all that apply.)
A. GTS
B. Advanced Busyout Monitor
C. RSVP
D. NBAR
E. Max Connections
F. AVBO.
Correct Answer: CEF Section: (none) Explanation
Explanation/Reference:
Explanation: http://www.cisco.com/en/US/customer/tech/ CK6 52/ CK7 01/technologies_white_paper09186a00800da467.shtm
QUESTION 14
What are the benefits, as listed in the DQOS course, for Enterprise Networks when QoS is implemented? (Choose all that apply.)
A. It decreases propagation delay.
B. It provides predictable response times.
C. It prevents the need to increase bandwidth.
D. It supports dedicated bandwidth per application.
E. It maximizes loss during bursty congestion.
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Explanation: QoS attemts to solve network traffic performance issues, although QoS is not a cure-all. To improve network performance, QoS features affect a network by manipulation the following network characteristics: 1) Bandwidth 2) Delay 3) Jitter (delay variation) 4) Packet loss Rerference: Cisco Press – DQOS Exam Certification Guide p.9
QUESTION 15
Which of the following is most likely to occur for voice in the absence of QoS? (Choose all that apply.)
A. choppy speech
B. words out of order due to recovery
C. disconnect calls
D. unsynchronized voice patterns
E. softer volume speech

Correct Answer: AC Section: (none) Explanation
Explanation/Reference:
Explanation: The following most likely occurs for voice in absence of QoS: Voice is hard to understand; voice breaks up, sounds choppy; calls are disconnected; large delay make it difficult to know when the other caller has finished talking. Rerference: Cisco Press – DQOS Exam Certification Guide p.765
QUESTION 16
Auto QoS is which type of Cisco IOS command?
A. interface
B. global
C. policy-map
D. service-map
E. serial interface only
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
To install the quality-of-service (QoS) class maps and policy maps created by the AutoQoS for the
Enterprise feature, use the auto qos command in interface configuration mode. To remove the QoS
policies, use the no form of this command.
Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/
products_command_reference_chapter09186a00801 a

QUESTION 17
Which two components are associated with the DiffServ model? (Choose two.)
A. hop-by-hop signaling
B. per-hop behavior
C. RSVP
D. Hard QoS
E. DSCP use of class selector
Correct Answer: BE Section: (none) Explanation
Explanation/Reference:
Explanation: The Differentiated Services (DiffServ) model describes services associated with traffic classes. Traffic classes are identified by the value of the DiffServ Code Point (DSCP replaces IP precedence in the ToS field of the IP header). The main goal of the DiffServ model are to provide scalability and a similar level of QoS to the Int Serv model, without having to do it on a per-flow basis. The network simply identifies a class (not application) and applies the appropriate per-hop behavior (QoS mechanism) Reference: Introduction to IP QoS (Course) p.34 Not A: DiffServ does not have signaling
QUESTION 18
What is true about a DSCP marked packet when it reaches an IP precedence based device?
A. The eight DSCP bits are all set to zero.
B. The last three bits of the DSCP are set to 101.
C. The 8 DSCP AF classes will be mapped into the 8 levels of IP precedence.
D. Bits 7-5 of DSCP have the same position and meaning as IP precedence.
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Reference: Cisco Press – DQOS Exam Certification Guide p.120
QUESTION 19
SIMULATION Simulation Exhibit:

You are working as a network administrator at Certkiller .com. You are required to configure the Certkiller 1 WAN edge router: you must configure the appropriate MQC based queuing mechanism for the outbound traffic to the WAN (S0/0) so that the following bandwidth requirements will be met. A strict priority queue with a 168 Kbps bandwidth guarantee for the class voice is reserved, a minimum bandwidth guarantee of 30 Kbps is configured for the class interactive, a minimum bandwidth guarantee of 16 Kbps for class bulk, and the default class is configured for WFQ with no bandwidth guarantee. In addition, also limit the bulk traffic class to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be). In addition, also limit the bulk traffic class to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be).
* Use a policy-map called “IIq-policy” and reference the existing class-maps already configured on the Certkiller 1 router.
Traffic Class Name Bandwidth Guarantee voice 168 Kbps maximum (use the IOS default burst value) interactive 30 Kbps minimum bulk 16 Kbps minimum (For the bulk traffic class, also limit the traffic to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be)) class-default Weighted Fair Queue with no bandwidth guarantee Simulation Output exhibit #1:

Simulation Output exhibit #2:

A.
B.
C.
D.
Correct Answer: Section: (none) Explanation
Explanation/Reference:
Certkiller 1(config)#policy-map llq-policy
Certkiller 1(config-pmap)#class voice
Certkiller 1(config-pmap-c)#priority 168
Certkiller 1(config-pmap-c)#class interactive
Certkiller 1(config-pmap-c)#bandwidth 30
Certkiller 1(config-pmap-c)#class bulk
Certkiller 1(config-pmap-c)#bandwidth 16
Certkiller 1(config-pmap-c)#shape average 2400
Certkiller 1(config-pmap-c)#class class-default
Certkiller 1(config-pmap-c)#fair-queue
Certkiller 1(config-pmap-c)#interface serial 0/0
Certkiller 1(config-if)#service-policy output llq-policy
Certkiller 1(config-if)#end
Certkiller 1#copy running-config startup-config

Explanation:
policy-map llq-policy (Not: iiq-policy)
shape average 24000 (not shape peak 24(shape in bps not kbps) and shape to average not peak)
Note: Uncertainty:
Actual exam problems:

1. Unable to use the command: fair-queue Note: There is no need to use the ip nbar protocol-discovery command as the question doesn’t state to configure NBAR.
QUESTION 20
Command exhibit: mis qos trust pass-through dscp Your apprentice Certkiller is configuring a Catalyst 2950 Switch. What is the purpose of the command she is submitting (see exhibit)?
A. The command configures a port to trust the incoming CoS and not modify the incoming DSCP when sending the frame out.
B. The command configures a port to trust the incoming CoS and to generate the internal DSCP based on the incoming CoS. The internalr DSCP will then determine the gress DSCP.
C. The command configures a port to trust the incoming CoS and DSCP values.
D. The command configures a port to trust the incoming CoS and to generate the internal DSCP based on the incoming DSCP. The internal DSCP will then determine the egress DSCP.
E. The command configures a port to trust the incoming CoS and bypass the CoS-to-DSCP maps for generating the internal DSCP.
F. The command configures a port to trust the incoming CoS and bypass the DSCP-to-CoS maps for generating the egress CoS.
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation: When the switch is in pass-through mode, it uses the CoS value of incoming packets without modifying the DSCP value and sends the packets from one of the four egress queues. By default, pass-through mode is disabled. The switch assigns a CoS value of 0 to all incoming packets without modifying the packets. The
switch offers best-effort service to each packet regardless of the packet contents or size an dends it from a
single egress queue.
To disable pass-through mode, use the no mls qos trust pass-ghrough dscp interface configuration
command.
Reference:
http://www.cisco.com/en/US/products/hw/switches/ps5213/products_configuration_guide_chapter09186a0

 
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