mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: Runs the following command on Router R1: R1# show…
A network engineer runs the following command on Router R1:
R1# show ipv6 interface tunnel 0
Tunnel0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::A8BB:CCFF:FE00:1
No global unicast address is configured
Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:1 MTU is 1480 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 milliseconds ND advertised retransmit interval is 0 milliseconds ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds Hosts use stateless autoconfiguration for addresses.
Based on this output, what is a likely problem?
⚠ Common exam trap
Cisco often tests the misconception that a link-local address alone is sufficient for IPv6 routing, but in fact, global unicast addresses are required for traffic to be routable beyond the local segment.
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 is not configured with a global IPv6 address, which may prevent routing of IPv6 traffic.
The output shows that the tunnel interface has no global unicast address configured, only a link-local address. Without a global IPv6 address, the router cannot route IPv6 traffic beyond the local link, as global reachability requires a globally routable address. This is a common misconfiguration in IPv6 tunneling scenarios where the tunnel source and destination are set but the interface itself lacks a global IPv6 address.
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 interface is down.
Why it's wrong here
The interface is up, line protocol is up.
- ✓
The tunnel is not configured with a global IPv6 address, which may prevent routing of IPv6 traffic.
Why this is correct
No global unicast address means the tunnel cannot be used for IPv6 routing beyond link-local.
- ✗
The MTU is too small for IPv6.
Why it's wrong here
1480 bytes is typical for tunnels; not a problem.
- ✗
IPv6 is not enabled on the tunnel.
Why it's wrong here
IPv6 is enabled as shown.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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