Page 185 - CISSO_Prep_ Guide

For the switch to route IP-based data to the device on the correct
port, the switch must know which IP address has been assigned
to the device. The switch creates a cross-reference table that lists
the IP addresses and their associated MAC addresses using
Address Resolution Protocol. ARP requests are broadcast by the
switch to the entire network; it manages to ask who is currently
associated with an IP address. The device that has been leased or
assigned that IP address will then reply by identifying its MAC
address. The switch keeps that in a table (cache) so that any
future traffic to that IP address can be routed to the correct
device.

ARP messages are unauthenticated, which can lead to data
compromise. A malicious person may send a reply to an ARP
broadcast, or even an unsolicited reply to the switch identifying