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--- arp [2025/10/04 11:30] – created plida
+++ arp [2025/10/04 11:58] (current) – plida
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+Source: https://www.fortinet.com/resources/cyberglossary/what-is-arp
 ====== ARP ======
 Address Resolution Protocol is used for discovering [[network-layer_datalink|Data Link layer]] addresses, like [[mac-address|MAC addresses]] from [[ip-address|IP addresses]]. It is used whenever a device wants to communicate with another device in the same LAN.
+ARP cache is created when an IP address is resolved. It is stored on any system in IPv4 Ethernet [[network|network]]. Entries can be made manually.
+ARP may be used as a simple announcement protocol.
+An ARP probe in IPv4 is an ARP request constructed with the SHA (Sender Hardware Address) of the probing hostand a TPA (Target protocol address) set to the IPv4 address being probed for. If some host on the network regards the IPv4 address as its own, it will reply to the probe (via the SHA of the probing host) thus informing the probing host of the address conflict.
+==== ARP types ====
+Proxy ARP is a technique by which a proxy device on a given network answers the ARP request for an IP address that is not on that network. The proxy is aware of the location of the traffic's destination and offers its own MAC address as the destination.
+Gratuitous ARP is almost like an administrative procedure, carried out as a way for a host on a network to simply announce or update its IP-to-MAC address. Gratuitous ARP is not prompted by an ARP request to translate an IP address to a MAC address.
+Host machines that do not know their own IP address could use the reverse address resolution protocol (RARP) for discovery: it is now obsolete.
+Whereas ARP uses an IP address to find a MAC address, inverse ARP uses a MAC address to find an IP address.