Arpwatch
Template:Short description Template:Infobox software Template:Lowercase arpwatch is a computer software tool for monitoring Address Resolution Protocol traffic on a computer network.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It generates a log of observed pairing of IP addresses with MAC addresses along with a timestamp when the pairing appeared on the network. It also has the option of sending an email to an administrator when a pairing changes or is added.
Network administrators monitor ARP activity to detect ARP spoofing, network flip-flops, changed and new stations and address reuse.
arpwatch was developed by Lawrence Berkeley National Laboratory, Network Research Group, as open-source software and is released under the BSD license.