Arp
From wikinotes
The Address Resolution Protocol maps MAC addresses to ipv4 addresses. If you are using IPV6, see nd instead.
Every host on a network maintains an arp cache. Entries are dated, and after a period of time they expire. After a host expires, it is re-queried to see if it still exists, and if so it's address is re-added to the arp table.
If you do not see a host in your arp table, you either:
- have not communicated with that host yet
- it's arp cache entry has expired
Attempting to ping addresses will add successful connections to the arp table.
