Editing Address Resolution Protocol (section)

==Example==
Two computers, ''A'' and ''B'', are connected to the same [[local area network]] with no intervening [[Gateway (telecommunications)|gateway]] or [[Router (computing)|router]]. ''A'' has a packet to send to IP address {{IPaddr|192.168.0.55}} which happens to be the address of ''B''.

Before sending the packet to ''B'', ''A'' broadcasts an ARP request message {{endash}} addressed with the broadcast MAC address {{MACaddr|FF:FF:FF:FF:FF:FF}} and requesting response from the node with IP address {{IPaddr|192.168.0.55}}. All nodes of the network receive the message, but only ''B'' replies since it has the requested IP address. ''B'' responds with an ARP response message containing its MAC addresses which ''A'' receives. ''A'' sends the data packet on the link addressed with ''B''{{'}}s MAC address.

Typically, network nodes maintain a [[lookup table|lookup]] cache that associates IP and MAC addressees. In this example, if ''A'' had the lookup cached, then it would not need to broadcast the ARP request. Also, when ''B'' received the request, it could cache the lookup to ''A'' so that if ''B'' needs to send a packet to ''A'' later, it does not need to use ARP to lookup its MAC address. Finally, when ''A'' receives the ARP response, it can cache the lookup for future messages addressed to the same IP address.<ref>{{cite book|last1=Chappell|first1=Laura A.|last2=Tittel|first2=Ed|title=Guide to TCP/IP|edition=Third|publisher=Thomson Course Technology|year=2007|pages=115–116|isbn=9781418837556}}</ref>