Inspect and act on the IPv6 neighbor table to diagnose local connectivity with `ip -6 neigh`. 28.01.2026 | reading time: 2 min A focused guide that shows how to inspect and manipulate the IPv6 neighbor table using the `ip -6 neigh` command so he can quickly diagnose link-local reachability and stale entries. Live example A workstation cannot reach a printer on the link; he inspects the neighbor table to see why and then forces a probe: ```bash $ ip -6 neigh show fe80::1 dev eth0 lladdr 00:11:22:33:44:55 REACHABLE fe80::2 dev eth0 lladdr 00:11:22:33:44:66 STALE fe80::3 dev eth0 INCOMPLETE ``` He then runs `ping6 -c1 fe80::3%eth0` which triggers Neighbor Solicitation and typically updates the INCOMPLETE entry to REACHABLE. State meanings INCOMPLETE means no link-layer address known yet, REACHABLE means recent confirmation, STALE means the entry exists but was not recently used, DELAY is a short wait before probing, PROBE means actively sending Neighbor Solicitation packets, and FAILED means resolution did not succeed; read states fast and act faster. Commands to act Common actions he will use: `ip -6 neigh show` to list, `ip -6 neigh flush all` to clear entries, `ip -6 neigh del <addr> dev eth0` to remove one, `ip -6 neigh replace <addr> lladdr <mac> dev eth0` to fix a mapping, and combine `dev` or `to` to filter the output; use these to force re-resolution or remove stale entries. Capture and verify When table inspection is not enough, capture Neighbor Discovery traffic with `tcpdump -i eth0 icmp6` or inspect packets in Wireshark; use `ndisc6` to send manual Neighbor Solicitations and watch for Neighbor Advertisements to verify behavior. Final thought Mastering the neighbor table is a small habit that prevents long troubleshooting nights; deepen his Linux networking skills and consider pursuing CompTIA Linux+ or LPIC-1, and use bitsandbytes.academy for focused exam preparation. Join Bits & Bytes Academy First class LINUX exam preparation. network utilities troubleshooting
