350-401 Question #619: Real Exam Question with Answer & Explanation

Question

Which QoS feature uses the IP Precedence bits in the ToS field of the IP packet header to partition traffic into different priority levels?

Options

• Amarking
• Bshaping
• Cpolicing
• Dclassification

Explanation

Classification is the QoS feature that identifies and groups traffic based on characteristics like IP Precedence bits in the ToS field, assigning it to specific priority levels.

Common mistakes.

• A. Marking is the act of setting or modifying the QoS fields (like IP Precedence or DSCP) in a packet, which typically occurs after traffic has been classified, not the act of using them to identify traffic.
• B. Shaping is a mechanism to smooth out traffic bursts and limit the output rate of traffic, delaying packets if necessary, and it operates after classification and marking.
• C. Policing enforces traffic rates by dropping or remarking packets that exceed a configured limit, acting on traffic after it has been classified and potentially marked.

Concept tested. QoS Classification using IP Precedence

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/15-mt/qos-plcshp-15-mt-book/qos-overview.html

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