The answer is that MPLS is not enabled on interface Gi0/2. When you run the show mpls forwarding-table command and see "Untagged" in the outgoing label column for a prefix, it indicates the outgoing interface or the next-hop router does not have MPLS enabled, so the router cannot impose a label and must forward the packet as a standard IP packet. In the Cisco CCNP ENARSI 300-410 exam, this output is a classic trap: many candidates mistakenly think "Untagged" means the label has been removed (like a PHP operation), but it actually signals a configuration failure—MPLS must be enabled under the interface with the mpls ip command. This tests your understanding of MPLS label imposition and the forwarding-table mechanics. A quick memory tip: "Untagged means unconfigured—if it’s not tagged, MPLS isn’t flagged."
300-410 MPLS L3VPN Practice Question
This 300-410 practice question tests your understanding of mpls l3vpn. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer runs the following command on Router PE6:
PE6# show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
16 Pop Label 10.0.0.1/32 0 Gi0/0 10.1.1.1
17 20 10.0.0.2/32 0 Gi0/1 10.2.2.2
18 Untagged 10.0.0.3/32 0 Gi0/2 10.3.3.3
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MPLS is not enabled on interface Gi0/2.
The MPLS forwarding table shows three entries. The third entry for prefix 10.0.0.3/32 has 'Untagged' as the outgoing label. This means the outgoing interface for that prefix does not have MPLS enabled, or the next hop does not support MPLS. This is a problem because MPLS packets cannot be forwarded with an untagged label.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
MPLS is not enabled on interface Gi0/2.
Why this is correct
The 'Untagged' label indicates MPLS is not enabled on the outgoing interface or the next hop is not an MPLS router.
Related concept
Read the scenario before looking for a memorised answer.
✗
The router has run out of local labels.
Why it's wrong here
Local labels 16, 17, 18 are assigned, so labels are available.
✗
Penultimate Hop Popping is misconfigured.
Why it's wrong here
PHP is correctly shown for the first entry; the issue is specific to the third entry.
✗
The prefix 10.0.0.3/32 is not reachable.
Why it's wrong here
The entry exists, so the prefix is reachable; the problem is with MPLS encapsulation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
PHP is correctly shown for the first entry; the issue is specific to the third entry.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
MPLS L3VPN — This question tests MPLS L3VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: MPLS is not enabled on interface Gi0/2. — The MPLS forwarding table shows three entries. The third entry for prefix 10.0.0.3/32 has 'Untagged' as the outgoing label. This means the outgoing interface for that prefix does not have MPLS enabled, or the next hop does not support MPLS. This is a problem because MPLS packets cannot be forwarded with an untagged label.
What should I do if I get this 300-410 question wrong?
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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