Click the exhibit button below. Traffic arriving at router PE 1 is marked with a dot1p value of 4. Given the network policies applied on the routers in the diagram below, what is the EXP value of…

Question

Exhibit

Options

• A2
• B3
• C5
• D6
• ENone of the above.

• A
  80% (28)
• B
  9% (3)
• C
  3% (1)
• D
  3% (1)
• E
  6% (2)

Explanation

Option A (EXP = 2) is correct because the network policies in the exhibit perform a two-stage QoS transformation: PE1's ingress classifier maps the incoming dot1p value of 4 to an internal forwarding class, and then the MPLS egress rewrite rule maps that forwarding class to an EXP value of 2 - the final remarked value that PE2 receives. The dot1p and EXP values are set by separate, independent policy stanzas, so the numbers do not carry over numerically.

Why the distractors fail:

• B (3) and D (6): Neither matches what the exhibit's rewrite policy outputs for the forwarding class that dot1p 4 resolves to.
• C (5): A tempting trap for anyone who assumes EXP = dot1p + 1 or some arithmetic offset - no such implicit relationship exists in MPLS QoS.
• E (None of the above): Incorrect; A is definitively supported by the shown policy.

Memory tip: Think of it as a relay race - dot1p hands the baton to a forwarding class at PE1 ingress, and the rewrite rule assigns the EXP at egress. The starting number (4) and the finishing number (2) are linked only through the policy table, never by arithmetic. On exam questions, always trace the full classify → remark chain rather than assuming input equals output.

No community discussion yet for this question.