350-501 Question #41: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. A network engineer is implementing QoS services. Which two statements about the QoS-group keyword on Cisco IOS XR 3re true? (Choose two )

Options

• AThe QoS group numbering corresponds to priority level
• BQoS group marking occurs on the ingress
• CIt marks packets for end to end QoS pokey enforcement across the network
• DQoS group can be used in fabric QoS policy as a match criteria
• EIt cannot be used with priority traffic class

Explanation

QoS group marking on Cisco IOS XR occurs on the ingress interface and can be subsequently used as match criteria in fabric QoS policies for consistent traffic treatment.

Common mistakes.

• A. QoS group numbering is an arbitrary identifier used for classification and does not inherently correspond to a specific priority level; priorities are determined by how these groups are used in policies.
• C. QoS group marking is primarily an internal classification mechanism for local QoS policy enforcement within a device or network segment, not an end-to-end marking for enforcement across an entire service provider network where DSCP or IP Precedence are typically used.
• E. QoS groups can indeed be used in conjunction with priority traffic classes; they serve as a classification method that can then feed into priority-based scheduling or queuing mechanisms.

Concept tested. Cisco IOS XR QoS group functionality

Reference. https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/qos/66x/b-qos-cg-ncs5500-66x/b-qos-cg-ncs5500-66x_chapter_010.html

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