6.7 ARP

The Address Resolution Protocol (ARP) enables hosts to convert a 32-bit IP address into a 48-bit Ethernet address (the MAC or "network card" address). ARP broadcasts a packet to all hosts attached to an Ethernet. The packet contains the desired destination IP address. Ideally, most hosts ignore the packet. Only the target machine with the correct IP address named in the packet should return an answer.

ARP spoofing is an attack that occurs when compromised nodes have access to the local area network. Such a compromised machine can emit phony ARP replies in order to mimic a trusted machine.