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300-410 Practice Question: The default tunnel mode for a tunnel interface on…

What is the default tunnel mode for a tunnel interface on Cisco IOS?

⚠ Common exam trap

Cisco often tests the assumption that the default tunnel mode is IPv6-in-IPv4 or GRE over IPv6, but the actual default is GRE over IPv4, which catches candidates who overlook the implicit IPv4 transport requirement.

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

✓

tunnel mode gre ip

The default tunnel mode on Cisco IOS is GRE (Generic Routing Encapsulation) over IPv4, configured with the command `tunnel mode gre ip`. This mode encapsulates packets using the GRE protocol (RFC 2784) with an IPv4 transport header, and it is the default when no explicit tunnel mode is specified. GRE ip supports multiprotocol payloads (IPv4, IPv6, etc.) and is widely used for site-to-site VPNs and overlay networks.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    tunnel mode ipv6ip

    Why it's wrong here

    ipv6ip is not the default.

  • ✓

    tunnel mode gre ip

    Why this is correct

    GRE over IPv4 is the default.

  • ✗

    tunnel mode gre ipv6

    Why it's wrong here

    GRE over IPv6 is not the default.

  • ✗

    tunnel mode mpls traffic-eng

    Why it's wrong here

    MPLS TE is a different tunnel mode.

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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.