NDP

Neighbor Discovery Protocol (NDP) is an IPv6 protocol that functions similarly to ARP.
It uses 5 ICMPv6 packets for router solicitation and neighbor discovery
- Router Solicitation (Type 133)
  - Hosts send RS messages when they first connect to a network to discover routers
- Router Advertisement (Type 134)
  - Routers advertise their presence with RA messages periodically
  - RAs are also sent in response to Router Solicitation packets
- Neighbor Solicitation (Type 135)
  - Used by nodes to determine the link-layer address of a neighbor
  - Also used to verify if a neighbor is still reachable
- Neighbor Advertisement (Type 136)
  - Sent in response to Neighbor Solicitation packets with information
  - Also sent unsolicited to provide new information quickly
- Redirect (Type 137)
  - Used by routers to redirect hosts to a better first-hop router

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