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300-410 Practice Question: In a manual IPv6 over IPv4 tunnel (tunnel mode…
In a manual IPv6 over IPv4 tunnel (tunnel mode ipv6ip), what is the default maximum number of hops (TTL) for the IPv4 header?
⚠ Common exam trap
Cisco often tests the distinction between the default TTL values for IPv6 (64) and the outer IPv4 header in a manual IPv6 over IPv4 tunnel (255), leading candidates to mistakenly choose 64 or 128.
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
✓
255
In a manual IPv6 over IPv4 tunnel (tunnel mode ipv6ip), the IPv4 header's TTL (Time to Live) defaults to 255. This is because the tunnel is treated as a directly connected virtual link, and the IPv4 TTL is set to the maximum value of 255 to minimize the chance of the tunneled packet being dropped due to TTL expiry within the transit IPv4 network. This behavior is defined in RFC 2473 and is the default for IPv6-in-IPv4 tunnels on Cisco IOS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
64
Why it's wrong here
64 is a common default for many protocols but not for manual tunnels.
- ✗
128
Why it's wrong here
128 is not the default for manual tunnels.
- ✓
255
Why this is correct
The default TTL is 255 for manual IPv6 over IPv4 tunnels.
- ✗
16
Why it's wrong here
16 is too low and not the default.
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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.