- A
The ISATAP interface is not enabled for IPv6 routing; 'ipv6 unicast-routing' is missing globally.
Why wrong: Incorrect. The global 'ipv6 unicast-routing' command enables IPv6 routing on the router; without it, the router wouldn't be able to ping the ISATAP server, but it can, so IPv6 routing is likely enabled.
- B
The ISATAP interface does not send router advertisements by default; the 'ipv6 nd ra-interval' command must be configured.
Why wrong: Incorrect. While ISATAP interfaces do not send Router Advertisements by default, the command 'ipv6 nd ra-interval' only adjusts the advertisement interval and does not enable RA generation. The correct fix involves configuring an IPv6 prefix or using 'ipv6 nd prefix'. Moreover, the problem states a static route is configured, so RA issues are secondary.
- C
The static route on the ISATAP router points to the wrong next-hop IPv6 address.
Correct. The static route points to the wrong next-hop IPv6 address, so packets from ISATAP hosts are forwarded incorrectly, preventing reachability to the native IPv6 network.
- D
The ISATAP tunnel source interface is not reachable from the ISATAP server.
Why wrong: Incorrect. The tunnel source interface is reachable because the router can ping the ISATAP server, indicating the tunnel is up and the source is reachable.
300-410 ISATAP 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. A key principle to apply: iSATAP. 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 an ISATAP tunnel on a router. The tunnel comes up and the router can ping the ISATAP server, but IPv6 hosts on the ISATAP network cannot reach IPv6 hosts on the native IPv6 network. The ISATAP router is configured with a static route to the native network. What is the most likely cause?
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 static route on the ISATAP router points to the wrong next-hop IPv6 address.
The ISATAP router has a static route to the native IPv6 network, but the hosts cannot reach it. Since the tunnel is up and the router can ping the ISATAP server, the tunnel itself is functional. The most likely issue is that the static route has an incorrect next-hop address, causing packets from the ISATAP hosts to be misdirected or dropped. While ISATAP interfaces do not send Router Advertisements by default, the absence of RAs would prevent hosts from learning a default route, but the question states a static route is configured, implying the router should forward traffic; however, if the route is wrong, forwarding fails. Option B is incorrect because 'ipv6 nd ra-interval' only sets the interval for RAs, not enabling them; the proper command to enable RAs is 'ipv6 nd prefix' or 'ipv6 address autoconfig'.
Key principle: ISATAP
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 ISATAP interface is not enabled for IPv6 routing; 'ipv6 unicast-routing' is missing globally.
Why it's wrong here
Incorrect. The global 'ipv6 unicast-routing' command enables IPv6 routing on the router; without it, the router wouldn't be able to ping the ISATAP server, but it can, so IPv6 routing is likely enabled.
- ✗
The ISATAP interface does not send router advertisements by default; the 'ipv6 nd ra-interval' command must be configured.
Why it's wrong here
Incorrect. While ISATAP interfaces do not send Router Advertisements by default, the command 'ipv6 nd ra-interval' only adjusts the advertisement interval and does not enable RA generation. The correct fix involves configuring an IPv6 prefix or using 'ipv6 nd prefix'. Moreover, the problem states a static route is configured, so RA issues are secondary.
- ✓
The static route on the ISATAP router points to the wrong next-hop IPv6 address.
Why this is correct
Correct. The static route points to the wrong next-hop IPv6 address, so packets from ISATAP hosts are forwarded incorrectly, preventing reachability to the native IPv6 network.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
ISATAP
- ✗
The ISATAP tunnel source interface is not reachable from the ISATAP server.
Why it's wrong here
Incorrect. The tunnel source interface is reachable because the router can ping the ISATAP server, indicating the tunnel is up and the source is reachable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many candidates assume the issue is RA-related because ISATAP tunnels don't send RAs by default, but the static route misconfiguration is a more direct cause when a route is explicitly configured.
Trap categories for this question
Command / output trap
Incorrect. The global 'ipv6 unicast-routing' command enables IPv6 routing on the router; without it, the router wouldn't be able to ping the ISATAP server, but it can, so IPv6 routing is likely enabled.
Detailed technical explanation
How to think about this question
ISATAP tunnels use a Non-Broadcast Multiple Access (NBMA) model where the tunnel interface is treated as a point-to-point link, so IPv6 Neighbor Discovery (ND) does not automatically send Router Advertisements. To enable RA generation, the interface must be configured with an IPv6 address and the 'ipv6 nd prefix' command to advertise the prefix, or the 'ipv6 address autoconfig' command to allow hosts to learn the prefix. In real-world scenarios, misconfigured RA suppression on tunnel interfaces is a common cause of IPv6 reachability failures, especially when migrating from IPv4 to IPv6 using ISATAP.
KKey Concepts to Remember
- ISATAP
- Static Route
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
ISATAP
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. ISATAP 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.
Review iSATAP, then practise related 300-410 questions on the same topic to reinforce the concept.
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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 — ISATAP.
What is the correct answer to this question?
The correct answer is: The static route on the ISATAP router points to the wrong next-hop IPv6 address. — The ISATAP router has a static route to the native IPv6 network, but the hosts cannot reach it. Since the tunnel is up and the router can ping the ISATAP server, the tunnel itself is functional. The most likely issue is that the static route has an incorrect next-hop address, causing packets from the ISATAP hosts to be misdirected or dropped. While ISATAP interfaces do not send Router Advertisements by default, the absence of RAs would prevent hosts from learning a default route, but the question states a static route is configured, implying the router should forward traffic; however, if the route is wrong, forwarding fails. Option B is incorrect because 'ipv6 nd ra-interval' only sets the interval for RAs, not enabling them; the proper command to enable RAs is 'ipv6 nd prefix' or 'ipv6 address autoconfig'.
What should I do if I get this 300-410 question wrong?
Review iSATAP, then practise related 300-410 questions on the same topic to reinforce the concept.
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?
ISATAP
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Last reviewed: Jun 24, 2026
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