LPIC-2 Advanced Networking Configuration Practice Question
An administrator wants to check the ARP cache for a specific IP address 192.168.1.1. Which command will display the ARP entry for that address?
⚠ Common exam trap
Test-takers frequently assume `arp -a` with an IP address works universally, but on Linux, `-a` expects a hostname and may fail silently or require DNS resolution, whereas `arp -n` with `grep` reliably filters numeric output without relying on name resolution.
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
✓
arp -n | grep 192.168.1.1
`arp -n` displays the ARP cache in numeric format, and piping it through `grep 192.168.1.1` filters the output to show only the entry for that specific IP address. The `-n` flag prevents reverse DNS lookups, ensuring the output contains raw IP addresses, which is essential for reliable filtering.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ip neigh show 192.168.1.1
Why it's wrong here
The correct syntax is 'ip neigh show | grep 192.168.1.1'; ip neigh show alone shows all.
- ✗
arp -a 192.168.1.1
Why it's wrong here
arp -a shows all entries with hostnames; to see specific, use arp -n and grep.
- ✓
arp -n | grep 192.168.1.1
Why this is correct
This filters the ARP cache for the specific IP.
- ✗
route -n
Why it's wrong here
This shows routing table, not ARP cache.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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