- A
Configuring the tunnel destination with the IPv4 address of the ISATAP client itself.
Correct. The tunnel destination should be the ISATAP router's IPv4 address, not the client's own address.
- B
Using a private IPv4 address as the tunnel source on the ISATAP router.
Correct. ISATAP requires a global IPv4 address for the tunnel source to ensure routability.
- C
Configuring the ISATAP interface ID as ::5EFE:xxxx.
Why wrong: Incorrect. The correct ISATAP interface ID is ::0200:5EFE:xxxx (includes the 0200: prefix).
- D
Setting the tunnel mode to ipv6ip.
Why wrong: Incorrect. The correct tunnel mode for ISATAP is tunnel mode ipv6ip isatap.
- E
Adding a static IPv6 route pointing to the ISATAP tunnel interface.
Why wrong: Incorrect. A static route is often required for ISATAP to direct traffic to the tunnel; its absence would not prevent formation but would affect forwarding.
Quick Answer
The answer is that using a private IPv4 address as the tunnel source on the ISATAP router will prevent the tunnel from forming correctly. This is because ISATAP relies on a globally routable IPv4 address for the tunnel source so that the client can reach the router; a private address is non-routable over the public internet, breaking the automatic mapping between the IPv4 address embedded in the ISATAP interface ID and the tunnel destination. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how ISATAP dynamically derives the destination from the interface ID—a common trap is confusing the tunnel source with the tunnel destination, which should never be manually set to the client’s own address. Remember that the ISATAP router must have a public source address, while the destination is automatically formed from the client’s embedded IPv4. A useful memory tip: “Source must be public, destination is automatic—never loop the client back.”
300-410 IPv6 Tunneling Techniques Practice Question
This 300-410 practice question tests your understanding of ipv6 tunneling techniques. 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.
Which TWO actions will prevent an ISATAP tunnel from forming correctly? (Choose TWO.)
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
Configuring the tunnel destination with the IPv4 address of the ISATAP client itself.
Option A is correct because in an ISATAP tunnel, the tunnel destination must be the IPv4 address of the ISATAP client (which is dynamically derived from the ISATAP interface ID). Configuring the tunnel destination with the client's own IPv4 address creates a loopback tunnel that cannot forward traffic, preventing the tunnel from forming correctly. The ISATAP router automatically derives the destination from the IPv4 address embedded in the ISATAP interface ID; manually setting it to the client's address breaks the automatic mapping.
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.
- ✓
Configuring the tunnel destination with the IPv4 address of the ISATAP client itself.
Why this is correct
Correct. The tunnel destination should be the ISATAP router's IPv4 address, not the client's own address.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Using a private IPv4 address as the tunnel source on the ISATAP router.
Why this is correct
Correct. ISATAP requires a global IPv4 address for the tunnel source to ensure routability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configuring the ISATAP interface ID as ::5EFE:xxxx.
Why it's wrong here
Incorrect. The correct ISATAP interface ID is ::0200:5EFE:xxxx (includes the 0200: prefix).
- ✗
Setting the tunnel mode to ipv6ip.
Why it's wrong here
Incorrect. The correct tunnel mode for ISATAP is tunnel mode ipv6ip isatap.
- ✗
Adding a static IPv6 route pointing to the ISATAP tunnel interface.
Why it's wrong here
Incorrect. A static route is often required for ISATAP to direct traffic to the tunnel; its absence would not prevent formation but would affect forwarding.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the tunnel destination must be explicitly configured, when in fact ISATAP automatically derives it from the interface ID, and manually setting it to the client's own address breaks the tunnel.
Detailed technical explanation
How to think about this question
ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) uses a modified EUI-64 interface identifier where the first 32 bits are 0000:5EFE (or 0200:5EFE) and the last 32 bits are the IPv4 address of the tunnel endpoint. The tunnel destination on the router is dynamically derived from this embedded IPv4 address, so manually setting it to the client's own address creates a self-referencing tunnel that cannot establish a valid adjacency. In real-world deployments, misconfiguring the tunnel destination is a common cause of ISATAP failure, especially when administrators attempt to statically define the destination instead of relying on automatic derivation.
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.
TExam Day Tips
- 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 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.
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FAQ
Questions learners often ask
What does this 300-410 question test?
IPv6 Tunneling Techniques — This question tests IPv6 Tunneling Techniques — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configuring the tunnel destination with the IPv4 address of the ISATAP client itself. — Option A is correct because in an ISATAP tunnel, the tunnel destination must be the IPv4 address of the ISATAP client (which is dynamically derived from the ISATAP interface ID). Configuring the tunnel destination with the client's own IPv4 address creates a loopback tunnel that cannot forward traffic, preventing the tunnel from forming correctly. The ISATAP router automatically derives the destination from the IPv4 address embedded in the ISATAP interface ID; manually setting it to the client's address breaks the automatic mapping.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 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.
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