List IPv6 LAN Neighbors with ndp -a

Inspect the Neighbor Discovery cache — the IPv6 equivalent of arp — on a Mac.

macOSndpipv6DiagnosticsMedium risk

Run `ndp -a` to print the IPv6 neighbor table with each neighbor's MAC and interface; `sudo ndp -c` clears it.

01Command

Command

$ ndp -a
# Clear the table and relearn:
sudo ndp -c

02What it does

macOS implements IPv6 via the BSD ndp tool, which shows the same kind of mapping `arp -a` gives for IPv4: link-local addresses, resolved MACs, and the network interface each entry learned from. This is the fastest way to see whether an IPv6 device is actually reachable — an entry in `REACHABLE` or `STALE` state proves two-way traffic happened. Prefixing `time` and rerunning reveals whether new neighbors are actively joining.

03Risk

RiskMedium risk

!Warning: Many modern networks are IPv6-first; troubleshooting with only arp -a misses half the traffic.

04Undo

✓No undo needed — this command does not change persistent state.

05Sources

NDP(8) — FreeBSD manual page
FreeBSD Project · technical · 2026-09-17
Evidence: Documents -a (list), -c (clear) and the Neighbor Discovery protocol mapping.

Last verified: 2026-09-17 · Category: Network

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