Remove stale Ethernet-to-IP mappings to restore connectivity or test neighbor discovery. 16.11.2025 | reading time: 2 min ARP entries bind IPv4 addresses to MAC addresses and sometimes go stale; clear them manually to force re-discovery and resolve transient connectivity issues. Live demo Show the neighbor table, flush it, and show the result with these commands: ```bash $ ip neigh 192.0.2.5 dev eth0 lladdr aa:bb:cc:dd:ee:ff REACHABLE $ sudo ip neigh flush all $ ip neigh ``` The second command removes dynamic ARP/neighbor entries; running `ip neigh` afterward typically yields an empty or much smaller table until traffic repopulates it. Targeted fixes Instead of flushing everything you can remove a single entry with `sudo ip neigh delete 192.0.2.5 dev eth0` or use the legacy tool `sudo arp -d 192.0.2.5` to delete one IPv4 ARP record; use `ip -6 neigh flush` for IPv6 neighbor caches. Key considerations Root privileges are required; NetworkManager or switch traffic will quickly repopulate entries, so clearing is temporary; flushing does not break established TCP sessions immediately but may cause delays while MAC addresses are relearned; on multi-homed hosts flush per interface with `ip neigh flush dev <if>` when appropriate. Related utilities Use `arping` to probe and repopulate entries, `ip` (iproute2) to inspect and manipulate neighbor state, and `arp` from net-tools for compatibility on older systems. Next steps Practice these commands in a lab, try targeted deletes and IPv6 neighbor operations, and add monitoring to detect repeated ARP issues; consider deepening your Linux skills and certifying with CompTIA Linux+ or LPIC-1 and prepare intensively at bitsandbytes.academy. Join Bits & Bytes Academy First class LINUX exam preparation. network troubleshooting utilities
