The following steps results in the generation of an ARP request packet:
The IP module sends a packet, destined for another host in the network, to the ARP module.
The ARP module looks up the ARP table (cache) to resolve the IP address.
If the supplied IP address is present in the ARP cache, it is resolved into its Ethernet address.
If the ARP module is not able to find an entry for this IP address in the ARP cache, then it sends an ARP request packet to the Ethernet driver, to resolve the IP address to the Ethernet address.
After the IP address is resolved by the ARP module, the packet is sent to the Ethernet driver for transmission.