Exam 300-420 topic 1 question 136 discussion

Actual exam question from Cisco's 300-420

Question #: 136
Topic #: 1

Refer to the exhibit. A customer needs to apply QoS to the network management traffic passing through the GigabitEthernet 0/2 interface. All eight queuing classes are in use, so the new requirement must be integrated into the existing policy. Which solution must the customer choose?

A. Mark the traffic to DSCP CS6 and assign it to the ROUTING class. Then, prioritize traffic within the class.
B. Mark the traffic to DSCP CS2 and assign it to the ROUTING class. Then, baseline existing queue sizes to determine if additional bandwidth can be provisioned to the ROUTING class.
C. Mark the traffic to DSCP CS4 and assign it to the SIGNALLING class. Then, prioritize traffic within the class.
D. Mark the traffic to DSCP CS5 and assign it to the SIGNALLING class. Then, baseline existing queue sizes to determine if additional bandwidth can be provisioned to the SIGNALLING class.

Show Suggested Answer

Suggested Answer: B 🗳️

by cwoolie at March 28, 2022, 3:40 p.m.

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neiker45

1 year ago

Selected Answer: B

In the link provided before, in figure 15-5 you can see how in the control queue they are doing the same thing we are doing here. They are taking network control, Internetwork control and network management traffic and putting them in one slot including their respective DSCP category. (https://www.ciscopress.com/articles/article.asp?p=2159353&seqNum=3).

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CKL_SG

1 year, 8 months ago

Selected Answer: B

Twelve-Class Egress Queuing Model Network control traffic (marked CS6), signaling traffic (marked CS3) and network management traffic (marked CS2) is all assigned to a dedicated nonpriority queue with a 10 percent bandwidth allocation; optionally, CS7 traffic may also be mapped to this queue. https://www.ciscopress.com/articles/article.asp?p=2159353&seqNum=3

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Eards

2 years, 3 months ago

Selected Answer: B

CS2 = mangement

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XalaGyan

2 years ago

Application PHB DSCP CoS Network Control - CoS 7 Internetwork Control CS6 48 CoS 6 Voice EF 46 CoS 5 Interactive-Video AF41 34 CoS 4 Streaming-Video CS4 32 CoS 4 Mission-Critical Data 25 CoS 3 Call-Signaling CS3 24 CoS 3 AF31 26 Transactional Data AF21 18 CoS 2 Network-Management CS2 16 CoS 2 Bulk Data AF11 10 CoS 1 Scavenger CS1 8 CoS 1 Best-Effort 0 0 0

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XalaGyan

2 years ago

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namibdigger

2 years, 6 months ago

Selected Answer: A

If i understand correctly i am asked to use the given classes and integrate it to the new policy - given I am not asked to alter the traffic values but to 'map' the network traffic to those values that are in the exibit it must be answer A. Answer B would be correct if i was allowed to alter the garantueed bandwith of the ROUTING class. I Think i am not allowed to do that so i would align with the given value of CS6 which is not 'normal' network mgmt but that value is due to alteration according to the customers requirements - so not sure what answer is expected

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XalaGyan

2 years ago

Great thinking but since CS6 is pretty much high prio or almost highest prio, i would refrain from using CS6 and CS7 entirely no matter what question or customer says. CS6 and CS7 should be left for the device to do its vital things. Eventhough Answer A looks good and namibdigger explained it well, i stick to Option B as it is less evil and gets the job done.

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iLikeHamburgers

2 years, 1 month ago

You make an interesting point. I hate this question because as you eluded to, it is not clear as to whether we can make changes to the existing config, the question only states that "it has to be integrated". I don't know how i'm supposed to interpret that. In the real world, you would be told explicitly whether changes can be implemented or not. The only other thing that comes to mind would be if you had to make changes throughout the entire network. Marking the mgmt traffic to CS6 would alleviate you from having to go into each and every device to make changes to the config. However the other side to that argument is you still have to go into every device to mark the mgmt traffic as CS6. Could we not just add this config class-map match-any ROUTING?? match ip dscp CS2

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certstudent2016

2 years, 9 months ago

Selected Answer: B

B seems correct https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/hcs/12_5/HCS_Solution/SRND/HCS_12_5_SRND/chcs_m_quality-of-service-considerations.pdf

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