ARP Simulator
Pick an address. Your laptop asks the whole LAN who has it.
Your cache is empty. Pick an address.
$ ip neigh
(empty)
What's inside the packet
Ask for an address first. The request and reply fields show up here.
ARP replies teach both sides. The device that answers saves your MAC from the request before it replies, so the reply needs no ARP of its own (RFC 826). Linux marks an entry STALE after roughly 30 seconds without confirmation, then checks it with one unicast request instead of a broadcast (ip-neighbour(8)).
Nerd tip: phones often use randomized MACs. The second hex digit of 3a:1f:6c:22:41:9d is a, so the locally administered bit is set. That address was never burned into a chip. Do it for real in Lab 05.