IPv6 Interface Autoconfiguration and Testing

In IPv6, an interface must always be configured with a link local address
- one or more routable addresses can be assigned to the interface in addition to the link local address
can either assign an IPv6 address:
- statically
  - generally reserved for routers and some types of servers
- using an automatic addressing scheme

Neighbor Discovery Protocol and Router Advertisements

Neighbor Discovery (ND) Protocol performs some functions on IPv6 that ARP and ICMP perform on IPv4
main functions of ND:
- address autoconfiguration
  - enables a host to configure IPv6 address for its interfaces automatically
  - can detect whether an address is already in use on the local network
    - uses neighbor solicitation (NS) and neighbor advertisement (NA) messages
- Prefix discovery
  - enables a host to discover the known network prefixes that have been allocated to the local segment
  - facilitates next-hop determination
    - whether a packet should be addressed to a local host or a router
  - uses router solicitation (RS) and router advertisement (RA) messages
    - RA contains information about:
      - the network prefixes served by the router
      - autoconfiguration options
      - link parameters (e.g., MTU and hop limit)
    - routers send RAs:
      - periodically
      - in response to a router solicitation initiated by the host
- Local address resolution
  - allows a host to discover other nodes and routers on the local network (neighbors)
  - process uses neighbor solicitation (NS) and neighbor advertisement (NA) messages
- Redirection
  - Enables a router to inform an host of a better route to a particular destination

while IPv4 uses link local addresses,
- these are not routable outside the local network
- needs DHCP for address autoconfiguration
IPv6 uses stateless address autoconfiguration (SLAAC)
- host generates a link local address and uses Neighbor Discovery (ND) messages to test that it is unique
- host listens for a router advertisement (RA) or transmits a router solicitation (RS) using ND protocol messaging
  - router can either:
    - provide a network prefix
    - direct the host to a DHCPv6 server to perform stateful autoconfiguration
    - perform some combination of stateless and stateful configuration