NDP (Neighbor Discovery Protocol)

Enable automatically neighbor discovery for IPv6 address

1. Router Discovery
   • a node can discover when it is connected to IPv6 Link — without the need of DHCP (Dynamic Host Configuration Protocol)
2. Network Prefix Discovery
   • When connect to IPv6 Link, can discover prefix assigned to that link
3. Parameter Discovery
   • Can automatically discover parameter such as MTU or next hop
4. Address Autoconfiguration
   • A node can determine its full address
5. Address resolution
   • A node can determine the link-layer next hop for a destination
6. Neighbor unreachability detection
7. Duplicate address detection
8. Redirect
   • Router can notify the host of a better next-hop than itself. It was path of ICMP in IPv4 but got moved to NDP in IPv6

NDP Message

1. Router Advertisement (RA):
   • Message are originated by routers to advertise their presence and other parameters like MTU, hop limits, etc
2. Router Solicitation (RS):
   • Messages originated from host to request a router to send an RA
3. Neighbor Solicitation (NS)
   • Messages are originated by nodes to request another nodes address for duplicate address detection and unreachability detection
4. Neighbor Advertisement (NA)
   • Messages are sent in response to NS message
5. Redirect
   • Messages are used for redirect purpose