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Exam A
QUESTION 1
Based on the following 2950 switch configurations, which statement is correct?
no wrr-queue cos-mapwrr-queue bandwidth 20 10 70 1wrr-queue cos-map 4 5wrr-queue cos-map 1 0 1 2 3wrr-queue cos-map 3 6 7
A. Queue 1 is setup as the expedite queue.
B. Queue 2 is setup as the expedite queue.
C. Queue 3 is setup as the expedite queue.
D. Queue 4 is setup as the expedite queue.
E. No queue is setup as the expedite queue.
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Explanation:
To allocate bandwidth between standard transmit queue 1 (low priority) and standard transmit queue 2 (high priority), use the wrr-queue bandwidth command. Use the no form of this command to return to the default settings.
wrr-queue bandwidth weight-1 weight-2 [ weight-3 ]no wrr-queue bandwidth
QUESTION 2
Refer to the exhibit. Which three statements are true about the configuration? (Choose three.)
class-map class-1match ip rtp 2024 1000
class-map class 2match dscp 5 6 7
policy-map access-group-1-traffic
class class-1
shape peak 16000
class class-2
police 8000 1000
conform-action set-dscp-transmit 1
exceed-action set-dscp-transmit 0
violate-action drop
class class-default
fair-queue 16
queue-limit 20
interface fastethernet 0/0service-policy output access-group1-traffic
A. Traffic that is subject to shaping can burst up to 32,000 bps.
B. IP traffic (DSCPs 5, 6, and 7) that is sent on fastethernet 0/0 will be traffic policed.
C. RTP traffic (ports 2024 and 1000) that is sent on fastethernet 0/0 will be traffic shaped.
D. Traffic that is subject to policing will have the DCSP set to 0 if the rate exceeds 1000 bps.
E. IP traffic (DSCPs 1, 2, 3, and 4) that is sent on fastethernet 0/0 are considered to have a violate status and are dropped.
F. IP traffic (DSCP 0) that is sent on fastethernet 0/0 will be subject to fair queuing.
Correct Answer: ABF Section: (none) Explanation Explanation/Reference:
QUESTION 3
Which two commands are typically applied to the voice traffic class within a policy-map? (Choose two.)
A. shape peak {bps}
B. priority {kbps}
C. bandwidth {kbps}
D. compress header ip rtp
E. random-detect ecn
F. random-detect dscp-based
Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
QUESTION 4
LAB Please click console
2950-SWITCH>en 2950-SWITCH#config terminal 2950-SWITCH(config)#int fa0/1 2950-SWITCH(config-if)#mls qos trust dscp 2950-SWITCH(config-if)#exit 2950-SWITCH(config)#int fa0/11 2950-SWITCH(config-if)#mls qos trust cos 2950-SWITCH(config-if)#exit 2950-SWITCH(config)#int fa0/10 2950-SWITCH(config-if)#mls qos trust cos 2950-SWITCH(config-if)#mls qos trust device cisco-phone 2950-SWITCH(config-if)#exit A.

B.
C.
D.
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Answer: Check certifyme eEngine, Download from Member Center
QUESTION 5
In which two locations is the qos pre-classify command applied to support QoS preclassification over an IPSec/GRE tunnel? (Choose two.)
A. the tunnel interface
B. the physical interface
C. the crypto map
D. the policy-map
E. the class-map
Correct Answer: AC Section: (none) Explanation
Explanation/Reference:
Explanation:
Configuring QoS for VPNs The QoS for VPNs feature, which is enabled by the qos pre-classify command, is restricted to tunnel and virtual template interfaces, and crypto map configuration submodes. For generic routing encapsulation (GRE) and IP in IP(IPIP) tunnel protocols, the qos pre-classify command is applied on the tunnel interface, making QoS for VPNs a configuration option on a per-tunnel basis.
For Layer 2 Forwarding(L2F) and Layer 2 Tunneling Protocol(L2TP) protocols, the qos pre-classify command is applied on the virtual template interface. L2TP clients belonging to identical virtual private dial-up network (VPDN) groups inherit the preclassification setting. The qos pre-classify command can be configured on a per-VPDN tunnel basis.
For IPSec tunnels, the qos pre-classify command is applied on the crypto map, allowing configuration on a per-tunnel basis. QoS features on the physical interface carrying the crypto map are able to classify packets before encryption.
The following example enables the QoS for Virtual Private Networks (VPNs) feature on tunnel interfaces and virtual templates:
Router(config-if)# qos pre-classify
The following example enables the QoS for VPNs feature on crypto maps:
Router(config-crypto- map)# qos pre-classify
QUESTION 6
What is the purpose of using multiactions traffic policing?
A. so that exceed traffic can be shaped and violate traffic can be policed
B. so that conform, exceed, and violate traffic can be marked with different CLPs
C. so that conform traffic from different flows can be marked with different DSCPs
D. so that class-based policing can mark at Layer 2 and Layer 3 at the same time
E. so that traffic can be policed using two separate rates
Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:
Multiactions traffic policing helps to class-based policing can mark at Layer 2 and Layer 3 at the same time.
QUESTION 7
What is the purpose of the qos pre-classify command?
A. to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header
B. to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C. to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP header
D. to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP header
E. to enable class-based marking on tunnel interface
F. to enable class-based marking on IPSec crypto maps
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
For Layer 2 Forwarding(L2F) and Layer 2 Tunneling Protocol(L2TP) protocols, the qos pre-classify command is applied on the virtual template interface. L2TP clients belonging to identical virtual private dial-up network (VPDN) groups inherit the preclassification setting. The qos pre-classify command can be configured on a per-VPDN tunnel basis. For IPSec tunnels, the qos pre-classify command is applied on the crypto map, allowing configuration on a per-tunnel basis. QoS features on the physical interface carrying the crypto map are able to classify packets before encryption. Reference: http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter0 9186a00800c75d3.html
QUESTION 8
Which QoS mechanism calculates the mean queue depth to determine its operation?
A. WRED
B. LLQ/CBWFQ
C. WFQ
D. class-based shaping
E. class-based policing
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
Weighted random early detection (WRED) is a queuing technique for congestion avoidance. WRED manages how packets are handled when an interface starts becoming congested. When traffic begins to exceed the interface traffic thresholds prior to any congestion, the interface starts dropping packets from selected flows. If the dropped packets are TCP, the TCP source recognizes that packets are getting dropped, and lowers its transmission rate. The lowered transmission rate then reduces the traffic to the interface, avoiding congestion. Because TCP retransmits dropped packets, no actual data loss occurs. WRED drops packets according to the following criteria: RSVP flows are given precedence over non-RSVP flows, to ensure that time-critical packets are transmitted as required. Using IP precedence or DSCP value of the packets, packets with higher precedence are less likely to be dropped. If the default settings are preventing QoS, the precedence value can be used to control how WRED determines when and how often to drop packets. The amount of bandwidth used by the traffic flow. Flows that use the most bandwidth are more likely to have packets dropped. The weight factor defined for the interface determines how frequently packets are dropped. WRED chooses the packets to drop after considering these factors in combination. The net result being that the highest priority and lowest bandwidth traffic is preserved. WRED differs from standard random early detection (RED) in that RED ignores IP precedence, and instead drops packets from all traffic flows, not selecting low precedence or high bandwidth flows. By selectively dropping packets before congestion occurs, WRED prevents an interface from getting flooded, necessitating a large number of dropped packets. This increases the overall bandwidth usage for the interface. An effective use of weighted random early detection is to avoid congestion on a predominantly TCP/IP network, one that has minimal UDP traffic and no significant traffic from other networking protocols. It is especially effective on core devices rather than edge devices, because the traffic marking performed on edge devices can then affect the WRED interfaces throughout the network. The disadvantage of WRED is that only predominantly TCP/IP networks can benefit. Other protocols, such as NetWare IPX/SPX, do not respond to dropped packets by lowering their transmission rates and just retransmit the packets at the same rate. WRED treats all non-TCP/IP packets as having precedence zero. In a mixed protocol environment, WRED might not be the best choice for queuing traffic. Weighted random early detection interfaces automatically favor high priority, low bandwidth traffic flows. No specific policies are needed. However, because WRED automatically uses the IP precedence settings in packets, consider marking all traffic that enters the device or mark the traffic at the point where it enters the network. Marking all traffic will ensure that packets receive the service level intended.
QUESTION 9
The following commands have been configured under the fa0/1 interface on the 2950 switch:
wrr-queue bandwidth 20 1 80 0mls qos trust cosmls qos trust device cisco-phone
Voice traffic from the IP phone that is directly connected to the fa0/1 interface is experiencing excessive delays.
What could be the cause of this problem?
A. The wrr-queue bandwidth weightings are not correct.
B. The default wrr-queue cos-map is being used.
C. The default cos-to-dscp map is being used.
D. The default dscp-to-cos map is being used.
E. The trust boundary configuration is not correct.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation:
Use the wrr-queue bandwidth global configuration command to assign weighted round robin (WRR) weights to the four class of service (CoS) priority queues. Use the no form of this command to disable the WRR scheduler and enable the strict priority scheduler.
wrr-queue bandwidth weight1…weight4no wrr-queue bandwidth
Use the show wrr-queue bandwidth user EXEC command to display the weighted round-robin (WRR) bandwidth allocation for the four class of service (CoS) priority queues.
QUESTION 10
Switch port fa0/2 has been configured to connect an IP phone with an attached PC. Given the set of commands shown below, where does the trust boundary lie?
interface fa0/2mls qos trust cosmls qos trust device cisco-phoneswitchport voice vlan 112
A. between the IP phone and the switch
B. between the IP phone and the PC
C. between the access layer switch and the distribution layer switch
D. between the PC port and the LAN port on the IP phone
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
In a typical network, you connect a Cisco IP Phone to a switch port. Traffic sent from the telephone to the switch is typically marked with a tag that uses the 802.1Q header. The header contains the VLAN information and the CoS 3-bit field, which determines the priority of the packet. For most Cisco IP Phone configurations, the traffic sent from the telephone to the switch is trusted to ensure that voice traffic is properly prioritized over other types of traffic in the network. By using the mls qos trust cos interface configuration command, you can configure the switch port to which the telephone is connected to trust the CoS labels of all traffic received on that port. In some situations, you also might connect a PC or workstation to the IP phone. In these cases, you can use the switchport priority extend cos interface configuration command to configure the telephone through the switch CLI to override the priority of the traffic received from the PC. With this command, you can prevent a PC from taking advantage of a high-priority data queue. However, if a user bypasses the telephone and connects the PC directly to the switch, the CoS labels generated by the PC are trusted by the switch (because of the trusted CoS setting) and can allow misuse of high-priority queues. The trusted boundary feature solves this problem by using the CDP to detect the presence of a Cisco IP Phone (such as the Cisco IP Phone 7910, 7935, 7940, and 7960) on a switch port. If the telephone is not detected, the trusted boundary feature disables the trusted setting on the switch port and prevents misuse of a high-priority queue.
Correct Answer:
Section: (none) Explanation Explanation/Reference:
QUESTION 12

Select and Place: Correct Answer:

Section: (none) Explanation
Explanation/Reference:
QUESTION 13
What does the following command accomplish?
router(config-pmap-c)# shape fecn-adapt
A. enables the router to lower the shaping rate when BECN bits are received
B. enables the router to lower the shaping rate when FECN bits are received
C. enables the router to respond to FECN bits by creating test frames in the opposite direction with the BECN bit set
D. enables the router to respond to BECN bits by creating test frames in the opposite direction with the FECN bit set
E. enables the router to increase the shaping rate when BECN bits are received
F. enables the router to increase the shaping rate when FECN bits are received
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 14
In a managed CE scenario, the customer’s network is supporting VoIP and bulk file transfers. According to the best practices, which QoS mechanisms should be applied on the WAN edge CE-PE 56-kbps Frame Relay link on the CE outbound direction?
A. WRR, FRTS, FRF.12, and CB-RTP header compression
B. WRR, CB-WRED, CB-Marking, FRF.12, and CB-RTP header compression
C. CBWFQ, CB-WRED, CB-Marking, CB-Policing, and FRTS
D. CBWFQ, FRTS, FRF.12, and CB-RTP header compression
E. LLQ, CB-WRED, CB-Marking, FRTS, FRF.12, and CB-RTP header compression
F. LLQ, CB-WRED, CB-Policing, and CB-TCP and CB-RTP header compressions
Correct Answer: E Section: (none) Explanation
Explanation/Reference:
Explanation:
1. WRED can be combined with CBWFQ. In this combination CBWFQ provides a guaranteed percentage of the output bandwidth, WRED ensures that TCP traffic is not sent faster than CBWFQ can forward it. The abbreviated configuration below shows how WRED can be added to a policy-map specifying CBWFQ:
Router(config)# policy-map prioritybwRouter(config-pmap)# class class-default fair-queueRouter(config-pmap-c)# class prioritytraffic bandwidth percent 40 random-detect
The random-detect parameter specifies that WRED will be used rather than the default tail-drop action.
2. The LLQ feature brings strict Priority Queuing (PQ) to CBWFQ. Strict PQ allows delay-sensitive data such as voice to be sent before packets in other queues are sent. Without LLQ, CBWFQ provides WFQ based on defined classes with no strict priority queue available for real-time traffic. For CBWFQ, the weight for a packet belonging to a specific class is derived from the bandwidth assigned to the class. Therefore, the bandwidth assigned to the packets of a class determines the order in which packets are sent. All packets are serviced fairly based on weight and no class of packets may be granted strict priority. This scheme poses problems for voice traffic that is largely intolerant of delay, especially variation in delay. For voice traffic, variations in delay introduce irregularities of transmission manifesting as jitter in the heard conversation. LLQ provides strict priority queuing for CBWFQ, reducing jitter in voice conversations. LLQ enables the use of a single, strict priority queue within CBWFQ at the class level. Any class can be made a priority queue by adding the priority keyword. Within a policy map, one or more classes can be given priority status. When multiple classes within a single policy map are configured as priority classes, all traffic from these classes is sent to the same, single, strict priority queue. Although it is possible to queue various types of real-time traffic to the strict priority queue, it is strongly recommend that only voice traffic be sent to it because voice traffic is well-behaved, whereas other types of real-time traffic are not. Moreover, voice traffic requires that delay be non- variable in order to avoid jitter. Real-time traffic such as video could introduce variation in delay, CertKiller.com thereby thwarting the steadiness of delay required for successful voice traffic transmission. When the priority command is specified for a class, it takes a bandwidth argument that gives maximum bandwidth in kbps. This parameter specifies the maximum amount of bandwidth allocated for packets belonging to the class configured. The bandwidth parameter both guarantees bandwidth to the priority class and restrains the flow of packets from the priority class. In the event of congestion, policing is used to drop packets when the bandwidth is exceeded. Voice traffic queued to the priority queue is UDP-based and therefore not adaptive to the early packet drop characteristic of WRED. Because WRED is ineffective, the WRED random-detect command cannot be used with the priority command. In addition, because policing is used to drop packets and a queue limit is not imposed, the queue-limit command cannot be used with the priority command.
QUESTION 15
In an unmanaged CE router implementation, how does the service provider enforce the SLA?
A. by using class-based policing on the CE to PE link to limit the customer’s input rate
B. by marking on the CE to PE link and using CBWFQ and CB-WRED on the PE to P link
C. by marking on the CE to PE link and using class-based policing on the PE to P link
D. by using class-based random discard on the CE to PE link to limit the customer’s input rate
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
In an unmanaged Router Implementation, Service provider can enforce SLA By using class based policy on the CE to PE link to limit the customer’s input rate.
QUESTION 16
Select and Place:

Correct Answer:
Section: (none) Explanation
Explanation/Reference:
QUESTION 17
A major media company recently deployed a new converged network. The original network design used separate networks for graphics and video, interactive data, and voice. The company has been experiencing problems with voice traffic in the new converged network. Most of the time voice quality is perfectly acceptable. Periodically voice quality exhibits unacceptable choppy voice signals, and occasionally calls are dropped. At this time the company is not willing to simply add bandwidth to the network.
Which QoS solution would most likely help to resolve the problem?
A. Use TCP header compression and LFI to reduce delays.
B. Prioritize voice traffic as the highest priority to ensure that voice traffic is always serviced by the priority queue.
C. Use advanced technologies to compress all video and graphics traffic on the network.
D. Use class-based weighted fair queuing to prioritize voice traffic with a higher weight than all other traffic.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation:
The need to prioritize packets arises from the diverse mixture of protocols and their associated behaviors found in the data networks of today. Different types of traffic that share a data path through the network can impact each other. Depending on the application and overall bandwidth, users may perceive performance degradation. Interactive audio data is delay sensitive, and transaction-based applications may require a higher priority than a file transfer. Videoconferencing requires a specified amount of bandwidth for acceptable performance. If the network is designed so that multiple protocols share a single data path between routers, prioritization may be necessary at the congestion points. Prioritization is most effective on WAN links where the combination of traffic bursts and relatively lower data rates can cause temporary congestion. Depending on the average packet size, prioritization is most effective when applied to links at T1/E1 bandwidth speeds or lower. If there is no congestion on the WAN link, traffic prioritization is not necessary. If a WAN link is constantly congested, traffic prioritization may not resolve the problem. Adding bandwidth might be the appropriate solution.
QUESTION 18
According to the best practices, in a service provider network, which statement is true as related to the QoS policy that should be implemented on the inbound provider (P) to provider (P) router link?
A. Traffic policing should be implemented to rate-limit the ingress traffic into the P router.
B. Because traffic should have already been policed and marked on the upstream ingress PE router, no input QoS policy is needed on the P to P link.
C. Class-based marking should be implemented because it will be needed for the class-based queuing that will be used on the P router output.
D. In the DiffServ model, all ingress and egress QoS processing are done at the network edge (for example, PE router), so no input or output QoS policy will be needed on the P to P link.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
QUESTION 19
Based on the configuration, which two statements are true? (Choose two.)

A. The interactive traffic class will have a minimum bandwidth guarantee of 256 kbps.
B. The interactive traffic class will have a maximum bandwidth guarantee of 256 kbps.
C. If the interactive traffic class exceeds an average rate of 256 kbps, the traffic rate will be throttled down to 128 kbps.
D. This configuration allows class-based traffic shaping to lower the traffic rate in response to the BECN bit.
E. The interactive traffic class will have a min-rate (min-cir) of 128 kbps.

Correct Answer: DE Section: (none) Explanation
Explanation/Reference:
QUESTION 20
Refer to the exhibit. According to the show output, which statement is true?

A. NBAR protocol discovery has been enabled on the router through the use of the match protocol commands within the class-map.
B. The unknown protocol traffic statistics refer to all the traffic matched by the class-default traffic class.
C. HTTP is the most active protocol on the Fa0/0 interface based on byte count.
D. The 5-minute average bits-per-second rate for all traffic entering the Fa0/0 interface is 398 kbps.
E. There is a total of 39,990 NetBIOS packets exiting the Fa0/0 interface.
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
The first step in being able to classify network traffic is to actually know what protocols and applications are running on the network. This knowledge enables administrators to prioritize business-critical information and applications over less-important applications. Unfortunately, to configure ACLs to classify network traffic you must have prior knowledge of the network applications, as well as their associated protocol or port numbers. One option for discovering the protocols currently traversing an interface within the network is using NBAR protocol discovery. NBAR is capable of recognizing any protocol included within the PDLM file. Protocol discovery is applied to the desired interface or group of interfaces using the following command at each intended interface:
ip nbar protocol-discovery
When protocol discovery is applied to the interface, statistics are gathered depicting the active protocols traversing the interface. To view the results of the protocol discovery process, use the following command:
show ip nbar protocol-discovery [ interface type num ]

 

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