Linux® Routing

Address Resolution Protocol (ARP)

The Address Resolution Protocol (ARP) maps Layer 3 IP addresses to Layer 2 MAC addresses. Understanding when and how ARP is used is important to fully utilize the arp command. Whenever a node wishes to send traffic to a particular IP address, it will use its own IP address and netmask to determine if the destination is on a directly connected network. If the destination address is not directly connected, the routing table is consulted. Assuming a route for the destination network exists (a default route can include the destination network), the host then determines the gateway for the routing entry. After the gateway is determined, an arp who-has request with the gateway’s (router) address can be broadcast on ...