Quick Answer
The answer is that the maximum number of IPv6 over IPv4 tunnels on a Cisco IOS router is platform-dependent, with no fixed software limit. This is correct because Cisco IOS does not impose a hard-coded maximum for IPv6 over IPv4 tunnels; instead, the actual limit is constrained by available system resources like CPU and memory, as well as the specific tunnel type—such as manual, 6to4, ISATAP, or GRE—and the complexity of the configuration. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding that scalability is tied to hardware capabilities rather than a universal number, often appearing as a trap where candidates assume a specific count like 16 or 256. A common memory tip is to remember that tunnels are like passengers on a bus: the bus (router) can carry as many as its engine (CPU) and seats (memory) allow, so there is no fixed ticket limit.
This 300-410 practice question tests your understanding of ipv6 tunneling techniques. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
What is the maximum number of IPv6 over IPv4 tunnels that can be configured on a Cisco IOS router?
256
Why wrong: No such fixed limit.
1024
Why wrong: No such fixed limit.
Platform-dependent, no fixed maximum.
The number is limited by memory and CPU.
64
Why wrong: No such fixed limit.
Answer choices
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
256
Why it's wrong here
No such fixed limit.
1024
Why it's wrong here
No such fixed limit.
Platform-dependent, no fixed maximum.
Why this is correct
The number is limited by memory and CPU.
Related concept
Read the scenario before looking for a memorised answer.
64
Why it's wrong here
No such fixed limit.
Common exam traps
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.
Detailed technical explanation
Under the hood, each IPv6 over IPv4 tunnel consumes a virtual interface (tunnel interface) and requires CPU cycles for encapsulation/decapsulation, as well as memory for routing tables and tunnel state. The actual limit is determined by the router's hardware specifications and the IOS feature set; for example, a high-end router like the ASR 1000 can support thousands of tunnels, while a low-end ISR might max out at a few hundred. In real-world scenarios, operators must monitor CPU utilization and memory usage to avoid performance degradation, as excessive tunnels can lead to packet drops or routing instability.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
IPv6 Tunneling Techniques — study guide chapter
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FAQ
IPv6 Tunneling Techniques — This question tests IPv6 Tunneling Techniques — Read the scenario before looking for a memorised answer..
The correct answer is: 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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