The QOS exam is one of the qualifying exams for the Cisco Certified Internetwork Professional, Cisco Certified Voice Professional, Cisco IP Telephony Design Specialist, Cisco IP Telephony Express Specialist, Cisco IP Telephony Operations Specialist, and Cisco IP Telephony Support Specialist certifications. The QOS 642-642 exam will test materials covered under the Implementing Cisco Quality of Service QOS v2.1 course. The exam will certify that the successful candidate has knowledge and skills necessary to configure and troubleshoot Cisco IOS routers running Quality of Service protocols in Service Provider and Enterprise environments. The exam covers topics on IP QOS, classification and marking Mechanisms, queuing mechanisms, traffic shaping and policing mechanisms, congestion avoidance mechanisms, link efficiency mechanisms, modular QOS command line interface, and QOS Best Practices.

1.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

Answer:C

2.What are two benefits of WFQ? (Choose two.)
A. WFQ is very easy to configure, and no manual traffic classification is necessary.
B. WFQ can provide fixed-bandwidth and fixed-delay guarantees.
C. WFQ can provide fixed-bandwidth guarantees.
D. WFQ can provide fixed-delay guarantees.
E. WFQ prevents the large-volume flows with large packet size from starving out the low-volume
flows with small packet size.
F. Based on DSCP, WFQ allows weighted, random dropping of packets when the WFQ system is
full.

Answer:AE

5.Which technology is required when configuring FRF.12 on a Cisco device?
A. FRF11.c
B. FRF.8
C. VoFR
D. MLP with interleaving
E. FRTS
F.  WRED

Answer:E

6.What are three methods of reducing delay for critical applications in a converged network?
(Choose three.)
A. Apply payload compression.
B. Increase link capacities.
C. Apply header compression.
D. Increase LFI fragment size.
E. Reduce inter-packet gaps.
F. Increase all queue depths.

Answer:ABC

7.At the network layer, IP packets are typically classified based on which three items? (Choose
three.)
A. packet length
B. VLAN Identifier
C. flow control bits
D. source and destination IP addresses
E. content of the ToS byte

Answer:ADE

8.What are three reasons link efficiency mechanisms are deployed on WAN links? (Choose three.)
A. decrease delay
B. decrease jitter
C. increase link speed
D. increase throughput
E. decrease propagation delay

Answer:ABD
Answer:ABD

9.Which mechanism is used for the prioritizing, protection, and isolation of traffic based on
marking?
A. classification and marking
B. congestion management
C. congestion avoidance
D. metering
E. policing
F. shaping
Answer:B

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