350-501 Question #246: Real Exam Question with Answer & Explanation

Question

The engineering team at a large ISP has been alerted a customer network is experiencing high traffic congestion. After a discussion between the ISP and technical personnel at the customer site, the team agrees that traffic to the customer network that exceeds a specific threshold will be dropped. Which task must the engineer perform on the network to implement traffic policing changes?

Options

• AConfigure RSVP to reserve bandwidth on all interfaces when a path is congested.
• BEnable Cisco Discovery Protocol on the interface sending the packets.
• CEnable Cisco Express Forwarding on the interfaces sending and receiving the packets.
• DSet IP precedence values to take effect when traffic exceeds a given threshold.

Explanation

To implement traffic policing that drops traffic exceeding a threshold due to congestion, the engineer must configure QoS policies to set IP precedence values or explicitly drop packets when the threshold is surpassed.

Common mistakes.

• A. RSVP is a protocol used for reserving bandwidth to guarantee quality of service for specific application flows, not for policing and dropping excess traffic that exceeds a defined threshold.
• B. Cisco Discovery Protocol (CDP) is a Layer 2 protocol used for discovering information about directly connected Cisco devices and is unrelated to traffic policing or congestion management.
• C. Cisco Express Forwarding (CEF) is a high-performance Layer 3 IP forwarding mechanism and does not directly implement traffic policing or congestion management policies, although it is an underlying forwarding service.

Concept tested. Traffic policing actions for exceeding thresholds (remarking/dropping)

Reference. https://www.cisco.com/c/en/us/td/docs/ios/qos/configuration/guide/12_4/qos_12_4_book/qos_pol_shaping.html

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