- A
The peer has the transform set with the same protocols but in a different order (ESP-AES-256 then ESP-SHA-HMAC), which is considered a mismatch.
IPsec transform sets are matched exactly, including the order of protocols.
- B
The peer uses ESP-AES-256 with a different key length, such as 128-bit.
Why wrong: AES-256 implies 256-bit key; AES-128 would be a different transform.
- C
The peer has 'crypto ipsec transform-set' with 'esp-sha-hmac' and 'esp-aes 256' but also includes 'comp-lzs'.
Why wrong: Extra protocols would also cause a mismatch, but the order issue is more subtle and common.
- D
The peer uses 'esp-sha-hmac' as authentication and 'esp-aes 256' as encryption, but the mode is set to transport instead of tunnel.
Why wrong: Mode mismatch is a separate issue and would show a different debug message.
Quick Answer
The answer is that the IPsec transform set mismatch occurs because the peer lists the same protocols—ESP-AES-256 and ESP-SHA-HMAC—but in a different order, which the Cisco IOS treats as a completely different transform set. During IPsec phase 2 negotiation, the transform set must match exactly on both peers, including the sequence of encryption and authentication protocols; swapping ESP-SHA-HMAC (authentication) before ESP-AES-256 (encryption) breaks the match, even though the individual algorithms are identical. On the Cisco CCNP ENARSI 300-410 exam, this is a classic trap designed to test your understanding that transform sets are order-sensitive, not just content-sensitive—a common misstep when troubleshooting VPN tunnels. Remember the memory tip: "Order is authority" for transform sets; if the peer lists encryption first, you must mirror that sequence exactly, or debug will always show a mismatch.
300-410 BGP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of bgp troubleshooting. 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.
An engineer configures IPsec with a transform set that includes ESP-SHA-HMAC and ESP-AES-256. The VPN tunnel fails to establish, and debug shows 'transform set mismatch'. What is the most likely explanation?
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.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The peer has the transform set with the same protocols but in a different order (ESP-AES-256 then ESP-SHA-HMAC), which is considered a mismatch.
The transform set must match exactly on both peers, including the order of protocols. ESP-SHA-HMAC is an authentication protocol, and ESP-AES-256 is encryption. If the peer has them in a different order or uses a different combination, the negotiation fails.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 peer has the transform set with the same protocols but in a different order (ESP-AES-256 then ESP-SHA-HMAC), which is considered a mismatch.
- ✗
The peer uses ESP-AES-256 with a different key length, such as 128-bit.
Why it's wrong here
AES-256 implies 256-bit key; AES-128 would be a different transform.
- ✗
The peer has 'crypto ipsec transform-set' with 'esp-sha-hmac' and 'esp-aes 256' but also includes 'comp-lzs'.
Why it's wrong here
Extra protocols would also cause a mismatch, but the order issue is more subtle and common.
- ✗
The peer uses 'esp-sha-hmac' as authentication and 'esp-aes 256' as encryption, but the mode is set to transport instead of tunnel.
Why it's wrong here
Mode mismatch is a separate issue and would show a different debug message.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
Mode mismatch is a separate issue and would show a different debug message.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
- →
BGP Troubleshooting — study guide chapter
Learn the concepts, then practise the questions
- →
BGP Troubleshooting practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 300-410 question test?
BGP Troubleshooting — This question tests BGP Troubleshooting — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The peer has the transform set with the same protocols but in a different order (ESP-AES-256 then ESP-SHA-HMAC), which is considered a mismatch. — The transform set must match exactly on both peers, including the order of protocols. ESP-SHA-HMAC is an authentication protocol, and ESP-AES-256 is encryption. If the peer has them in a different order or uses a different combination, the negotiation fails.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.