Configure Explicit Trust at the DiffServ Trust Boundary (F and G)

Design end-to-end QoS policies
Answer Correct answer: B — Ports F and G are the trust boundary where access-layer traffic (already classified) enters the DiffServ domain, so explicit trust is set there.

Refer to the exhibit. Which two points in the network must an engineer configure the ports for explicit trust when using a DiffServ model? - image

  1. B and E
  2. F and G Correct Answer
  3. A and D
  4. C and D

Community Votes

B
75%
A
25%

75% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

Set explicit trust at the ingress edge of the trusted domain — where marked traffic from the access layer enters (F, G). Interior/core links already carry trusted marking and do not need a new trust boundary.

Under a DiffServ model, the trust boundary is where untrusted or already-classified traffic enters the trusted QoS domain. Points F and G are the edge ports where access-layer traffic (already marked) enters, so the engineer configures explicit trust there to honor the received markings.

Picking A (B and E): those are deeper in the fabric where traffic is already trusted; the explicit-trust boundary is at the access edge (F, G) where markings first enter the DiffServ domain.

Community Discussion (3 comments)

salmarin 👍 1 Selected: B
F-G as traffic already classified by the access layer
RexChen 👍 1 Selected: A
i think it's A
TheGorn 👍 2 Selected: B
https://networklessons.com/quality-of-service/how-to-configure-qos-trust-boundary-on-cisco-switches

Comments & Corrections

No comments yet — spotted an error or have a note? Share it below.

Log in to comment, report an error, or add a note about this question.

Submitted for moderation before publishing. Keep it helpful and respectful.

Expert Analysis

Why the Answer Is Correct

B is correct. F and G are the edge ports where traffic from the access layer (already classified/marked) enters the trusted DiffServ domain, so explicit trust is configured there to accept and honor the received DSCP/CoS markings.

Why the Other Options Are Wrong

A (B and E) places the trust boundary deeper in the fabric where traffic is already trusted and classified, which is not where an explicit trust boundary is needed. C (A and D) and D (C and D) are interior points, not the access-edge ingress where trust must be set.

Community Comment Notes

The vote is B (75) vs A (25). Commenters state F and G are correct because traffic is already classified by the access layer as it enters those ports.

Related Analysis

An engineer is designing a QoS solution for a customer. The

S-Grade

Refer to the exhibit. A company specializing in VoD content

A-Grade

Refer to the exhibit. An architect is designing a Layer 3 ca

S-Grade

Practice All 300-420 Questions

Access 150 questions with complete answers and detailed explanations.

View Full 300-420 Practice Test →

← Back to 300-420 Study Guide