This prints the kernel's neighbor table, mapping every recently contacted LAN address to its MAC address, interface, and state. Entries marked REACHABLE are freshly confirmed, while STALE ones await revalidation. It is the iproute2 replacement for arp -a and the first place to look when two machines cannot talk.
Looking for more? Search all 7,657 commands — works offline, in English or Spanish, and fixes typos.