The ARP table stores pairs of IP and MAC addresses. This storage saves time and communication costs, since the host looks in the ARP table first when transmitting a packet. If the information is not there, then the host sends an ARP Request.

There are two types of entries in the ARP table:

Static ARP table entries Static ARP table entries do not expire.

Dynamic ARP table entries Dynamic ARP table entries are mappings between IP addresses and MAC addresses that the switch used recently. Dynamic ARP table entries expire after a configurable amount of time. The following diagram shows how a switch adds dynamic ARP table entries: