This chapter looks at what we consider to be ‘essential’ functions and services of IPv6. In other words, without these functions and services we would not be able to achieve satisfactory IPv6 operation (or even no connectivity at all). First, we briefly describe Neighbour Discovery and look at several router configurations. Next we detail how DNS works in IPv6 and describe how this worked in the 6NET network. Finally, we describe DHCPv6 along with several available implementations.