easyMultiple Choice
300-410 Practice Question: The maximum number of IPv6 over IPv4 tunnels that…
What is the maximum number of IPv6 over IPv4 tunnels that can be configured on a Cisco IOS router?
⚠ Common exam trap
Cisco often tests the misconception that there is a fixed numerical limit (like 256, 1024, or 64) for IPv6 over IPv4 tunnels, when in fact the correct answer is that the limit is platform-dependent and resource-driven.
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
✓
Platform-dependent, no fixed maximum.
C is correct because the maximum number of IPv6 over IPv4 tunnels on a Cisco IOS router is platform-dependent and limited by available system resources such as CPU and memory, not by a fixed software limit. Cisco IOS does not impose a hard-coded maximum; the actual number depends on the router model, the type of tunnel (e.g., manual, 6to4, ISATAP, GRE), and the configuration complexity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
256
Why it's wrong here
Cisco IOS supports a maximum of 1024 tunnel interfaces, so 256 understates the platform limit. It is tempting because 256 matches common per-interface or per-VRF sub-limits, but the question asks for the total tunnel-interface ceiling, which is 1024.
- ✗
1024
Why it's wrong here
Cisco IOS supports a maximum of 1000 IPv6-over-IPv4 tunnels, not 1024. The figure is tempting because it resembles a plausible power-of-two limit, but the actual configured tunnel-interface ceiling is 1000, so 1024 exceeds the supported maximum.
- ✓
Platform-dependent, no fixed maximum.
Why this is correct
Cisco IOS imposes no fixed protocol-level ceiling on IPv6 over IPv4 tunnel interfaces; the practical limit depends on the platform's memory, interface capacity and hardware resources. The maximum is therefore platform-dependent rather than a universal number.
- ✗
64
Why it's wrong here
Cisco IOS permits up to 1024 tunnel interfaces, so 64 is far below the platform ceiling. It is tempting because 64 resembles limits for other features such as HSRP groups or VLANs, but those are unrelated to the tunnel-interface maximum.
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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.