LPIC-2 Advanced Networking Configuration Practice Question
An administrator is troubleshooting IPv6 connectivity on a Linux host. The host has an IPv6 address configured on eth0, but cannot ping6 the default gateway. The output of 'ip -6 route show' shows a default route via fe80::1 dev eth0. Which tool should be used to verify that the neighbor discovery process is working?
⚠ Common exam trap
A common mix-up: candidates confuse the Linux command 'ip neigh show' with the BSD command 'ndp -n', or they think that packet capture (tcpdump) is the only way to diagnose NDP issues, when in fact the neighbor cache provides a direct snapshot of the resolution state.
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
✓
ip neigh show
The 'ip neigh show' command displays the neighbor cache (equivalent to ARP table for IPv6), which is populated by the Neighbor Discovery Protocol (NDP). Since the default gateway is a link-local address (fe80::1), the host must have resolved the gateway's MAC address via NDP before it can send packets. If the neighbor entry is missing or incomplete (e.g., STALE or FAILED), it indicates that the neighbor discovery process is not working, which would explain the ping failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
tcpdump -i eth0 icmp6
Why it's wrong here
While this can capture neighbor solicitation/advertisements, it is not a quick verification tool.
- ✗
traceroute6
Why it's wrong here
traceroute6 tests path, but not neighbor discovery for the first hop.
- ✓
ip neigh show
Why this is correct
This shows the neighbor discovery cache, including unresolved entries.
- ✗
ndp -n
Why it's wrong here
ndp is a FreeBSD command, not available on Linux.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.