300-420 Question #138: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. A customer needs to apply QoS to the network management traffic passing through the GigabitEthernet0/2 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?

Options

• AMark traffic to DSCP CS5 and assign it to the SIGNALLING class. Then, baseline existing queue
• BMark the traffic to DSCP CS4 and assign it to the SIGNALLING class. Then, prioritize traffic within
• CMark the traffic to DSCP CS6 and assign it to the ROUTING class. Then, prioritize traffic within
• DMark the traffic to DSCP CS2 and assign it to the ROUTING class. Then, baseline existing queue

Explanation

{"question_number": 7, "question": "A customer needs to apply QoS to the network management traffic passing through the GigabitEthernet0/2 interface. All eight queuing classes are in use...", "correct_answer": "D", "explanation": "Per the IETF and Cisco QoS design guidelines, network management traffic (SNMP, SSH, Telnet, syslog) is marked DSCP CS2 (DSCP decimal 16). Since all eight queuing classes are already in use, the management traffic must be merged into an existing class. The ROUTING class is the appropriate fit because it already handles control-plane adjacent traffic. Assigning minimum bandwidth (not a strict-priority queue) ensures management traffic gets a guaranteed share without starving other classes. 'Baselining existing queue assignments' means recording what bandwidth each existing class currently uses before redistribution - you need this baseline to safely reallocate bandwidth when adding the new traffic. Options A and B use CS5/CS4 which are reserved for voice signaling and video, respectively. Option C uses CS6 which is reserved for routing protocol traffic (OSPF, BGP hellos), not management.", "generated_by": "claude-sonnet", "llm_judge_score": 3}

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