Quick Answer
The answer is that EIGRP for IPv6 adjacencies are established over the tunnels. This is correct because the output of show ipv6 eigrp neighbors displays two neighbors with link-local addresses (FE80::/10) on interfaces Tunnel0 and Tunnel1, with increasing sequence numbers and active hold timers, which confirms that the IPv6 EIGRP adjacency is fully formed and exchanging routes over those tunnel interfaces. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret neighbor table output and distinguish between a formed adjacency and a mere configuration; a common trap is assuming that seeing a neighbor entry always means the adjacency is up, but the presence of a non-zero Seq Num and active uptime is the key confirmation. Remember the memory tip: “Link-local on a tunnel means the adjacency is a funnel”—if you see FE80 addresses on a tunnel interface with active counters, the adjacency is live and exchanging routes.
This 300-410 practice question tests your understanding of ipv6 tunneling techniques. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
A network engineer runs the following command on Router R1:
R1# show ipv6 eigrp neighbors
IPv6-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 FE80::A8BB:CCFF:FE00:2 Tunnel0 13 00:23:45 10 200 0 12 1 FE80::A8BB:CCFF:FE00:3 Tunnel1 12 00:22:10 15 200 0 15
Based on this output, which statement is correct?
EIGRP is not configured for IPv6.
Why wrong: Neighbors are shown, so EIGRP for IPv6 is configured.
The neighbors are using global unicast addresses.
Why wrong: The addresses are link-local (FE80::/10).
EIGRP for IPv6 adjacencies are established over the tunnels.
Neighbors are present with uptime and hold time.
The tunnels are using GRE encapsulation.
Why wrong: The output does not specify encapsulation type.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
EIGRP for IPv6 adjacencies are established over the tunnels.
The output shows two IPv6 EIGRP neighbors with link-local addresses (FE80::/10) on interfaces Tunnel0 and Tunnel1, and the adjacency is established and exchanging routes (Seq Num increasing). This confirms that EIGRP for IPv6 adjacencies are formed over these tunnel interfaces, making option C correct.
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.
EIGRP is not configured for IPv6.
Why it's wrong here
Neighbors are shown, so EIGRP for IPv6 is configured.
The neighbors are using global unicast addresses.
Why it's wrong here
The addresses are link-local (FE80::/10).
EIGRP for IPv6 adjacencies are established over the tunnels.
Why this is correct
Neighbors are present with uptime and hold time.
Related concept
Read the scenario before looking for a memorised answer.
The tunnels are using GRE encapsulation.
Why it's wrong here
The output does not specify encapsulation type.
Common exam traps
Cisco often tests the misconception that EIGRP for IPv6 uses global unicast addresses for neighbor adjacencies, but the output clearly shows link-local addresses, and candidates may incorrectly assume the tunnels must be GRE without evidence from the command output.
Trap categories for this question
Command / output trap
Neighbors are shown, so EIGRP for IPv6 is configured.
Detailed technical explanation
EIGRP for IPv6 forms adjacencies using link-local addresses by default, as defined in RFC 7868, and the 'show ipv6 eigrp neighbors' command displays these link-local addresses. The Hold timer (13 and 12 seconds) indicates the adjacency is stable, and the SRTT and RTO values show low latency, typical for tunnel interfaces. In real-world scenarios, tunnels are often used to connect non-contiguous IPv6 domains over an IPv4 backbone, and EIGRP for IPv6 can run over these tunnels to exchange routing information.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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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: EIGRP for IPv6 adjacencies are established over the tunnels. — The output shows two IPv6 EIGRP neighbors with link-local addresses (FE80::/10) on interfaces Tunnel0 and Tunnel1, and the adjacency is established and exchanging routes (Seq Num increasing). This confirms that EIGRP for IPv6 adjacencies are formed over these tunnel interfaces, making option C correct.
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
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