Which of these is the iproute2 replacement for `arp -n`, showing the mapping of neighbouring IP addresses to their MAC addresses?
LPIC-1 Exam 102-500, objective 109. Networking fundamentals medium
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The options
Correct ip neigh show
Correct. `ip neigh show` (also `ip n s`, or `ip neighbour show`) prints the kernel's neighbour table: the IPv4 ARP and IPv6 neighbour-discovery entries with their link-layer addresses and states such as REACHABLE or STALE.
Not correct ip link show
Wrong. `ip link show` lists the local interfaces and their own MAC addresses and flags, not the addresses of other hosts on the segment.
Not correct ip route get
Wrong. `ip route get DESTINATION` asks the kernel which route and source address it would use for one destination. It answers a routing question, not a link-layer one.
Not correct ip maddr show
Wrong. `ip maddr` lists multicast group memberships of the interfaces, which is a different table entirely.
Why
The neighbour table caches which MAC address answers for a given IP on the local link, learned via ARP for IPv4 and neighbour discovery for IPv6. Two hosts showing the same MAC for different addresses, or an entry stuck in FAILED, points at a duplicated address or an unreachable neighbour. Delete a stale entry with `ip neigh del ADDRESS dev IFACE`; the old net-tools equivalents are `arp -n` and `arp -d`.
Where this comes from
- Cited
- manual page ip-neighbour(8)
Practise this
Reading one question is not practice. The trainer will draw a set from objective 109 and space the ones you get wrong.