350-801 Question #398: Real Exam Question with Answer & Explanation

Question

A collaboration engineer is configuring the QoS trust boundary for Cisco UCM voice and video conferencing. Which two trust boundary configurations are valid? (choose two)

Options

• AQoS trust boundaries include all the devices directly attached to the access switch ports
• BQoS trust boundaries can be extended to Jabber running on a PC
• CQoS trust boundaries exclude Jabber softphone running on a PC
• DQoS trust boundaries can be extended to voice and video devices if the connected PCs are
• EQoS trust boundaries can be extended to voice and video devices exclusively

Explanation

The QoS trust boundary should ideally be set at the first network device that can classify and mark traffic, typically the IP Phone, and should not be extended to a PC running a softphone directly, but can include other voice/video devices if managed correctly.

Common mistakes.

• A. Extending QoS trust boundaries to all devices directly attached to access switch ports is too broad and risky, as many end devices cannot be trusted to mark traffic correctly.
• B. Extending QoS trust boundaries directly to Jabber running on a PC is not recommended due to the untrusted nature of PC operating systems and their susceptibility to QoS marking manipulation.
• E. Stating that QoS trust boundaries can be extended to voice and video devices exclusively is not entirely accurate, as the boundary typically starts at the IP phone and the decision to extend depends on specific network design and trust models for other devices.

Concept tested. QoS trust boundary placement for collaboration endpoints

Reference. https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_QoS/QoSDesignGuide/QoSDesignGuide.html

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