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300-410 Practice Question: An engineer is troubleshooting an IPv6 deployment…
An engineer is troubleshooting an IPv6 deployment where hosts on a subnet are not receiving IPv6 addresses via SLAAC. The router is configured with 'ipv6 unicast-routing' and the interface has 'ipv6 address 2001:db8:1::1/64' and 'ipv6 nd other-config-flag'. The hosts are sending Router Solicitations but receive no Router Advertisements. What is the root cause?
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 'ipv6 nd ra suppress' command is configured on the interface.
For SLAAC to work, the router must send Router Advertisements (RAs). The 'ipv6 nd other-config-flag' only sets the 'O' flag for additional information (like DNS), but does not enable RA generation. The interface must have an 'ipv6 enable' command or a configured unicast address to automatically enable RA generation, but here the address is configured, so RA generation should be on by default. However, the 'ipv6 nd prefix' command may be missing or the interface may be administratively down. The most common cause is that the interface is not 'no shutdown' or the RA interval is set to 0. Given the symptom, the likely cause is that the interface is in a state where RAs are suppressed, such as when 'ipv6 nd ra suppress' is configured.
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 interface is missing the 'ipv6 enable' command.
Why it's wrong here
Incorrect because 'ipv6 enable' is not required if an IPv6 address is already configured; the address itself enables IPv6 on the interface.
- ✓
The 'ipv6 nd ra suppress' command is configured on the interface.
Why this is correct
Correct because this command suppresses Router Advertisements, preventing hosts from receiving RAs even though the interface has an IPv6 address.
- ✗
The 'ipv6 nd prefix' command is missing for the subnet.
Why it's wrong here
Incorrect because by default, the router advertises the prefix configured on the interface; a specific 'ipv6 nd prefix' command is only needed to modify advertisement parameters.
- ✗
The hosts are using DHCPv6 instead of SLAAC.
Why it's wrong here
Incorrect because the issue is that no RAs are received, which is required for both SLAAC and DHCPv6 stateless; the symptom points to RA suppression.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.