The figure shows two potential issues with ARP.
Overhead on the Media
As a broadcast frame, an ARP request is received and processed by every device on the local network. On a typical business network, these broadcasts would probably have minimal impact on network performance. However, if a large number of devices were to be powered up and all start accessing network services at the same time, there could be some reduction in performance for a short period of time. For example, if all students in a lab logged into classroom computers and attempted to access the Internet at the same time, there could be delays. However, after the devices send out the initial ARP broadcasts and have learned the necessary MAC addresses, any impact on the network will be minimized.
In some cases, the use of ARP can lead to a potential security risk. ARP spoofing, or ARP poisoning, is a technique used by an attacker to inject the wrong MAC address association into a network by issuing fake ARP requests. An attacker forges the MAC address of a device and then frames can be sent to the wrong destination.
Manually configuring static ARP associations is one way to prevent ARP spoofing. Authorized MAC addresses can be configured on some network devices to restrict network access to only those devices listed.