350-401 Question #1309: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. What is the expected behavior of the QoS policy if a new flow of traffic was sent out this interface at 192 kbps and was marked with a value of DSCP34?

Options

• AThis traffic would be assigned to the default queue and would experience drops.
• BThis traffic would match the overall shape rate of 256 kbps and be transmitted without drops
• CThis traffic would be assigned to the default queue and would only experience drops if the remaining
• DThis traffic is out of profile for the QoS policy and should be assigned to a separate priority queue

Explanation

If the QoS policy's overall shaping rate for the interface is 256 kbps, a new traffic flow of 192 kbps will operate within the configured limits and be transmitted without drops due to shaping.

Common mistakes.

• A. Traffic is only assigned to the default queue if it does not match any other defined class, and it would only experience drops if the default queue itself is congested or oversubscribed, not simply because it's 192 kbps.
• C. While traffic not matching a specific class goes to the default queue, whether it experiences drops depends on the overall interface congestion and the policies applied to the default class, and this statement is incomplete.
• D. Traffic being 'out of profile' typically refers to exceeding a defined rate for a specific class. If the traffic rate (192 kbps) is below the interface's shaping limit (256 kbps), it is not necessarily out of profile for the overall policy, nor would it automatically be assigned to a 'separate priority queue'.

Concept tested. QoS traffic shaping behavior

Reference. https://www.cisco.com/c/en/us/td/docs/ios/qos/configuration/guide/qos_c/qoscshpe.html

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