hardMultiple SelectObjective-mapped
Manual IPv6-in-IPv4 Tunnel Configuration and TTL
Which TWO statements about IPv6 manual tunnels (IPv6-in-IPv4) are true? (Choose TWO.)
Quick Answer
The correct answer is that the tunnel interface requires both an IPv4 address and an IPv6 address, because a manual IPv6-in-IPv4 tunnel encapsulates IPv6 packets directly into IPv4 packets using protocol type 41, as defined in RFC 4213, meaning the tunnel source and destination must be IPv4 while the traffic inside is IPv6. This configuration is explicitly set with the `tunnel mode ipv6ip` command, which distinguishes it from other tunnel types like GRE or 6to4. On the Cisco CCNP ENARSI 300-410 exam, this topic tests your understanding of IPv6 transition mechanisms and often appears as a trap where candidates confuse manual tunnels with automatic 6to4 tunnels—remember that manual tunnels require explicit IPv4 addresses on both ends, while 6to4 uses an IPv6 prefix derived from the IPv4 address. A key memory tip: think of the manual tunnel as a direct point-to-point IPv4 “pipe” carrying IPv6, so both address families must be configured on the tunnel interface.
⚠ Common exam trap
Cisco often tests the distinction between manual tunnels and automatic 6to4 tunnels, where candidates mistakenly think the IPv4 source address is embedded in the IPv6 prefix (true for 6to4) or that multicast destinations are allowed (true for GRE tunnels, not manual IPv6-in-IPv4).
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 tunnel mode must be configured as tunnel mode ipv6ip.
The `tunnel mode ipv6ip` command explicitly configures the tunnel interface for IPv6-in-IPv4 manual tunneling. This mode encapsulates IPv6 packets directly into IPv4 packets using protocol type 41, as defined in RFC 4213. Without this mode, the tunnel interface would not properly handle the encapsulation and decapsulation of IPv6 traffic over an IPv4 infrastructure.
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 tunnel mode must be configured as tunnel mode ipv6ip.
Why this is correct
Correct. Manual IPv6-in-IPv4 tunnels use tunnel mode ipv6ip.
- ✓
The tunnel interface requires both an IPv4 address and an IPv6 address.
Why this is correct
Correct. The tunnel interface must have an IPv4 address (or source/destination) for the outer header and an IPv6 address for the inner payload.
- ✗
Manual tunnels support multicast traffic natively.
Why it's wrong here
Incorrect. Manual tunnels are point-to-point and do not support multicast; GRE tunnels are required for multicast.
- ✗
The tunnel destination can be a multicast IPv4 address.
Why it's wrong here
Incorrect. Manual tunnels require a unicast IPv4 destination address.
- ✗
The IPv4 address of the tunnel source is automatically embedded in the IPv6 prefix.
Why it's wrong here
Incorrect. That behavior is for 6to4 tunnels, not manual tunnels. Manual tunnels use explicit addressing.
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Same concept, more angles
2 more ways this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Consider this configuration on Router R5: ``` interface Tunnel0 ipv6 address 2001:DB8:7::1/64 tunnel source 192.168.10.1 tunnel destination 192.168.20.2 tunnel mode ipv6ip tunnel ttl 64 ``` What is the effect?
medium- A.The tunnel will not work because the tunnel source is an IP address, not an interface.
- ✓ B.The tunnel will work, and the TTL field in the outer IPv4 header will be set to 64.
- C.The tunnel mode should be 'gre ip' for IPv6 over IPv4.
- D.The tunnel will use the IPv6 TTL for the outer header.
Why B: The configuration creates an IPv6-over-IPv4 manual tunnel (tunnel mode ipv6ip). The tunnel source is specified as an IP address, which is valid; the router uses that address as the source of the outer IPv4 header. The 'tunnel ttl 64' command explicitly sets the Time-to-Live field in the outer IPv4 header to 64, overriding the default value.
Variation 2. Given this configuration on Router R3: ``` interface Tunnel0 no ip address ipv6 address 2001:DB8:5::1/64 tunnel source 192.168.1.1 tunnel destination 192.168.2.2 tunnel mode ipv6ip ``` What is missing or incorrect?
medium- A.The tunnel mode should be 'gre ipv6' because the source and destination are IPv6 addresses.
- B.The tunnel interface must have an IPv4 address.
- C.The tunnel source should be an interface, not an IP address.
- ✓ D.The configuration is correct and will function as an IPv6 over IPv4 tunnel.
Why D: The configuration uses 'tunnel mode ipv6ip', which is a valid manual IPv6-over-IPv4 tunnel. The source and destination are IPv4 addresses, as required for this tunnel mode. No changes are needed; the tunnel will function correctly for IPv6 over IPv4 transport.
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.