IPv6 Neighbor Discovery: Life After ARP

In IPv4, we use the Address Resolution Protocol (ARP) to find a device's MAC address. In IPv6, ARP is gone. It has been replaced by the more efficient Neighbor Discovery Protocol (NDP).

No More Broadcasts

ARP relies on broadcasts (shouting to everyone). NDP uses Multicast, which is much more efficient because only the devices that need to listen actually wake up to process the packet.

Router Solicitation

NDP allows a device to find its way off the local network automatically. When a device joins, it sends a Router Solicitation (RS) message, and the router replies with a Router Advertisement (RA) containing the network settings.

This "plug and play" nature is what makes IPv6 much easier to manage at scale than IPv4.