The correct answer is that the same EVI must be used on both PEs, as an EVI mismatch is the most likely cause of an EVPN-VPWS pseudowire not coming up. In EVPN-VPWS, the EVI (Ethernet VPN Instance) acts as the service identifier that must match on both endpoints to establish the pseudowire; if the EVI values differ, the control plane cannot correlate the two sides of the point-to-point service, leaving the pseudowire down. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of EVPN service instantiation—a common trap is confusing EVI with ESI, but remember that a non-zero ESI is required for VPWS, while the EVI must be identical on both PEs. A helpful memory tip: "EVI must be identical" — think of it as the matching service ID that bridges the two endpoints, just like a VLAN ID must match on both sides of a traditional pseudowire.
350-501 Architecture Practice Question
This 350-501 practice question tests your understanding of architecture. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 service provider is deploying EVPN-VPWS for point-to-point services. They have set up an EVPN instance with Ethernet Segment Identifier (ESI) and EVI. After configuration, the pseudowire is not coming up. Which misconfiguration is most likely?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
In EVPN-VPWS, the EVI must match on both endpoints; otherwise, the pseudowire cannot be established.
B
The ESI is all-zeros.
Why wrong: While a zero ESI is invalid, the pseudowire would still attempt to form if ESI is non-zero; a zero ESI would not be the most likely cause if it were configured incorrectly.
C
The MTU mismatch on the attachment circuits.
Why wrong: MTU mismatch can cause packet drops but is not the most likely reason for the pseudowire not coming up at the control plane level.
D
The BGP EVPN address-family is not activated.
Why wrong: If BGP EVPN AF is not activated, no EVPN routes would be exchanged, impacting all services, not just VPWS.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The same EVI is used on both PEs.
Option B is correct because for EVPN-VPWS, the same EVI must be used on both PEs to establish the pseudowire. Option A is wrong because a non-zero ESI is required, but all-zeros is invalid. Option C is wrong because BGP EVPN address-family is needed but its absence would affect all EVPN services, not just VPWS. Option D is wrong because MTU mismatch causes issues but is less likely than EVI mismatch.
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.
✓
The same EVI is used on both PEs.
Why this is correct
In EVPN-VPWS, the EVI must match on both endpoints; otherwise, the pseudowire cannot be established.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ESI is all-zeros.
Why it's wrong here
While a zero ESI is invalid, the pseudowire would still attempt to form if ESI is non-zero; a zero ESI would not be the most likely cause if it were configured incorrectly.
✗
The MTU mismatch on the attachment circuits.
Why it's wrong here
MTU mismatch can cause packet drops but is not the most likely reason for the pseudowire not coming up at the control plane level.
✗
The BGP EVPN address-family is not activated.
Why it's wrong here
If BGP EVPN AF is not activated, no EVPN routes would be exchanged, impacting all services, not just VPWS.
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.
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 350-501 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.
What to study next
Got this wrong? Here's your next step.
Identify which 350-501 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.
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The same EVI is used on both PEs. — Option B is correct because for EVPN-VPWS, the same EVI must be used on both PEs to establish the pseudowire. Option A is wrong because a non-zero ESI is required, but all-zeros is invalid. Option C is wrong because BGP EVPN address-family is needed but its absence would affect all EVPN services, not just VPWS. Option D is wrong because MTU mismatch causes issues but is less likely than EVI mismatch.
What should I do if I get this 350-501 question wrong?
Identify which 350-501 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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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