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300-410 Practice Question: Is troubleshooting an IPv6 over IPv4 tunnel using…
A network engineer is troubleshooting an IPv6 over IPv4 tunnel using Teredo on a Windows host. The host can access some IPv6 resources on the internet but cannot reach a specific internal IPv6 server. The engineer suspects the Teredo relay is misconfigured. What is the most likely issue?
⚠ Common exam trap
Cisco often tests the distinction between Teredo relay and Teredo server roles, and the trap here is that candidates confuse a misconfigured relay (which affects specific destinations) with a misconfigured server (which breaks all Teredo connectivity).
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 Teredo relay is not in the same IPv4 network as the host, or the relay does not have a route to the internal IPv6 server.
Teredo relays are responsible for forwarding traffic between the Teredo IPv6 tunnel and the native IPv6 network. If the relay is not on the same IPv4 subnet as the host or lacks a route to the internal IPv6 server, the host can reach public IPv6 resources (via other relays) but fails to reach the internal server. This matches the symptom of partial connectivity.
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 Teredo relay is not in the same IPv4 network as the host, or the relay does not have a route to the internal IPv6 server.
Why this is correct
Correct because the Teredo relay must be able to forward packets to the destination IPv6 network. If the relay lacks a route, traffic will be dropped.
- ✗
The host's firewall is blocking Teredo traffic on UDP port 3544.
Why it's wrong here
Incorrect because the host can access some IPv6 resources, so Teredo is working for those destinations; the issue is specific to the internal server.
- ✗
The internal server is not configured with an IPv6 address.
Why it's wrong here
Incorrect because the server is reachable via other means (e.g., IPv4), but the question states the host cannot reach it via IPv6.
- ✗
The Teredo client on the host is using an incorrect server.
Why it's wrong here
Incorrect because the Teredo server is used for address assignment, not for forwarding traffic to native IPv6 networks.
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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.