- A
The crypto map on the spoke uses a dynamic map, but the hub is configured with a static crypto map entry for the spoke, causing a mismatch in the IPsec negotiation.
In DMVPN, the hub typically uses a static crypto map with multiple peers, while spokes use a dynamic crypto map to accept connections from any hub. If the spoke incorrectly uses a static map, or the hub uses a dynamic map, the negotiation fails.
- B
The transform set uses ESP-AES-256-SHA, but the hub is configured with ESP-AES-256-SHA-HMAC, causing a mismatch in the authentication algorithm.
Why wrong: SHA and SHA-HMAC are essentially the same; this would not cause a mismatch.
- C
The IPsec pre-shared key is configured correctly, but the ISAKMP policy uses aggressive mode, which is incompatible with DMVPN.
Why wrong: Aggressive mode can be used in DMVPN, though main mode is more common; it is not inherently incompatible.
- D
The spoke's tunnel interface is not in 'ip nhrp network-id' mode, causing NHRP to fail and IPsec to not trigger.
Why wrong: NHRP network-id is required for DMVPN, but its absence would cause NHRP failure, not a crypto map mismatch.
Quick Answer
The answer is a mismatch between the spoke’s dynamic crypto map and the hub’s static crypto map entry for the spoke. In a DMVPN Phase 2 network, the hub typically uses a static crypto map with a specific peer address and an access-list defining interesting traffic, while the spoke often relies on a dynamic crypto map to accept connections from multiple peers. When the spoke’s crypto map is dynamic but the hub’s static map does not include a matching entry for that spoke, IPsec negotiation fails with the ‘no matching crypto map entry’ error, even if transform sets like ESP-AES-256-SHA are identical. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how DMVPN crypto maps must align between hub and spoke—a common trap is assuming identical transform sets guarantee success, while the real issue lies in the map type or the ‘match address’ access-list defining the tunnel network as interesting traffic. Remember the mnemonic: “Static hub, dynamic spoke—if the map type’s broke, the tunnel’s a joke.”
300-410 DMVPN Practice Question
This 300-410 practice question tests your understanding of dmvpn. 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 on a DMVPN Phase 2 network using a transform set with ESP-AES-256-SHA. The hub and spokes are configured identically. Unexpectedly, the IPsec tunnel fails to establish, and debug output shows 'no matching crypto map entry' on the spoke. Which 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 crypto map on the spoke uses a dynamic map, but the hub is configured with a static crypto map entry for the spoke, causing a mismatch in the IPsec negotiation.
In DMVPN, the crypto map is applied to the tunnel interface. However, if the spoke's crypto map does not match the hub's due to a missing or mismatched 'match address' access-list (interesting traffic definition), the IPsec tunnel will not initiate. The corner case is that in DMVPN, the interesting traffic is typically defined by the tunnel network itself (e.g., IPsec protects traffic between tunnel IPs). If the access-list uses the wrong source/destination, or if the crypto map is not correctly applied to the tunnel interface, the IPsec negotiation fails. Additionally, if the crypto map uses dynamic maps for the spoke, but the hub is configured with a static map, a mismatch can occur.
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 crypto map on the spoke uses a dynamic map, but the hub is configured with a static crypto map entry for the spoke, causing a mismatch in the IPsec negotiation.
Why this is correct
In DMVPN, the hub typically uses a static crypto map with multiple peers, while spokes use a dynamic crypto map to accept connections from any hub. If the spoke incorrectly uses a static map, or the hub uses a dynamic map, the negotiation fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
The transform set uses ESP-AES-256-SHA, but the hub is configured with ESP-AES-256-SHA-HMAC, causing a mismatch in the authentication algorithm.
Why it's wrong here
SHA and SHA-HMAC are essentially the same; this would not cause a mismatch.
- ✗
The IPsec pre-shared key is configured correctly, but the ISAKMP policy uses aggressive mode, which is incompatible with DMVPN.
Why it's wrong here
Aggressive mode can be used in DMVPN, though main mode is more common; it is not inherently incompatible.
- ✗
The spoke's tunnel interface is not in 'ip nhrp network-id' mode, causing NHRP to fail and IPsec to not trigger.
Why it's wrong here
NHRP network-id is required for DMVPN, but its absence would cause NHRP failure, not a crypto map mismatch.
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.
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.
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FAQ
Questions learners often ask
What does this 300-410 question test?
DMVPN — This question tests DMVPN — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The crypto map on the spoke uses a dynamic map, but the hub is configured with a static crypto map entry for the spoke, causing a mismatch in the IPsec negotiation. — In DMVPN, the crypto map is applied to the tunnel interface. However, if the spoke's crypto map does not match the hub's due to a missing or mismatched 'match address' access-list (interesting traffic definition), the IPsec tunnel will not initiate. The corner case is that in DMVPN, the interesting traffic is typically defined by the tunnel network itself (e.g., IPsec protects traffic between tunnel IPs). If the access-list uses the wrong source/destination, or if the crypto map is not correctly applied to the tunnel interface, the IPsec negotiation fails. Additionally, if the crypto map uses dynamic maps for the spoke, but the hub is configured with a static map, a mismatch can occur.
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.
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Last reviewed: Jun 18, 2026
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