Arpwatch
Template:Short description {{#invoke:Infobox|infobox}}Template:Template other{{#invoke:Check for unknown parameters | check | showblankpositional=1 | unknown = Template:Main other | preview = Page using Template:Infobox software with unknown parameter "_VALUE_"|ignoreblank=y | AsOf | author | background | bodystyle | caption | collapsetext | collapsible | developer | discontinued | engine | engines | genre | included with | language | language count | language footnote | latest preview date | latest preview version | latest release date | latest release version | latest_preview_date | latest_preview_version | latest_release_date | latest_release_version | licence | license | logo | logo alt | logo caption | logo upright | logo size | logo title | logo_alt | logo_caption | logo_upright | logo_size | logo_title | middleware | module | name | operating system | operating_system | other_names | platform | programming language | programming_language | released | replaced_by | replaces | repo | screenshot | screenshot alt | screenshot upright | screenshot size | screenshot title | screenshot_alt | screenshot_upright | screenshot_size | screenshot_title | service_name | size | standard | title | ver layout | website | qid }}Template:Main other 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.