Chapter 15 / 15.4 / 15.4.3

15.4.3 Address Resolution

Although routers make forwarding decisions using IP addresses, data-link networks require physical addresses to deliver frames locally.

For example, Ethernet uses MAC addresses to identify devices on a LAN. Before transmitting a frame, the sender must therefore determine the MAC address corresponding to the destination IP address.

In IPv4 networks this function is performed by the Address Resolution Protocol (ARP). IPv6 provides an equivalent capability through the Neighbor Discovery Protocol (NDP), which forms part of the Internet Control Message Protocol Version 6 (ICMPv6).

These protocols operate automatically and are normally invisible to network users. Their purpose is simply to map logical IP addresses to the physical addresses required by the local communication technology.