350-801 Question #253: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An engineer must modify the existing QoS policy-map statement to implement LLQ for voice traffic. Which change must the engineer make in the configuration?

Options

• Abandwidth 170 to LLQ 170
• Bbandwidth 170 to priority 170
• Cbandwidth 170 to reserve 170
• Dbandwidth 170 to percent 170

Explanation

To implement Low Latency Queuing (LLQ) for voice traffic within a QoS policy-map, the priority command with a specified bandwidth value is used to reserve a strict priority queue.

Common mistakes.

• A. The term LLQ itself is a feature, not a command used to replace bandwidth in a policy-map for configuration; priority is the correct command for strict priority queuing.
• C. The reserve command is not a standard QoS command used in policy-maps to implement LLQ; priority is the correct command for strict priority queuing.
• D. The percent keyword is typically used with the bandwidth command (e.g., bandwidth percent 170) to allocate a percentage of available bandwidth, which is not what LLQ achieves, as LLQ provides strict priority, not just a guaranteed percentage.

Concept tested. Cisco QoS Low Latency Queuing (LLQ) configuration

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_congest/configuration/xe-16-7/qos-congest-xe-16-7-book/qos-congest-xe-16-7-book_chapter_010.html

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