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Routing & Switching · Intermediate

QoS Trust Boundary

The point in the network where QoS markings from endpoints start being trusted rather than rewritten.

Definition

Ideally the trust boundary is at the access switch or the IP phone. Untrusted endpoints have markings reset to 0 or reclassified. Cisco switches can extend trust to a phone via CDP while not trusting the attached PC.

Example

trust device cisco-phone on a Catalyst access port

Exam tip

Placing the trust boundary at the PC lets users mark their own traffic as EF; exams say place it at the phone or access switch.

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