Brad Bonkoski wrote: > I know what ARP is.... > Gratuitous ARP as defined in TCP/IP ILLUSTRATED VOL.1, The Protocols by W. > Richard Stevens > "It occurs when a host sends an ARP request looking for its own IP address. > This is usually done when the interface is configured at bootstrap time." > Now, to me, that sounds like RARP, bootp, etc... but I could be wrong. So, > I ask you all. Gratuitous ARP is used *after* the interface is configured, while RARP is used in order to obtain the IP address with which to configure the interface. Note that a gratuitous ARP request will have both sender and target IP address fields filled in (with the same address), while a RARP request has neither. The aforementioned part of Stevens goes on to give the reasons behind gratuitous ARP, which are basically: 1. To determine if any other host is using the IP address; if the sender receives a reply, it logs an error message. 2. In case either the IP address or MAC address has changed. The gratuitous ARP request should replace any previous entries in other hosts' ARP caches. -- Glynn Clements <glynn.clements@virgin.net> - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
