Summary
Highlights
With stateful DHCPv6, the router directs the host to a DHCPv6 server, which assigns both the IPv6 address and other configuration details (like DNS). The DHCPv6 server maintains a record of all assigned information.
IPv6 addresses include unicast, multicast, and anycast types. Unicast addresses are sent to a single host. There are three types of unicast addresses: link-local, unique local, and global unicast addresses.
Link-local addresses (LLA) are used only within a local area network (LAN) for communication between devices on the same link. They are similar to private IPv4 addresses but are confined to a single link. LLAs always begin with FE80.
Unique local addresses are also private addresses but allow communication between private LANs. However, they cannot be routed on the internet. These addresses start with FC or FD.
Global unicast addresses (GUA) are publicly routable internet addresses, comparable to public IPv4 addresses. Typically, hosts are assigned a link-local address for internal communication and a global unicast address for external communication. GUAs start with 2 or 3.
Multicast addresses send packets to a group of users, replacing the broadcast functionality of IPv4. Multicast addresses start with FF. Anycast addresses are unicast addresses assigned to multiple interfaces, where packets are routed to the nearest interface with that address.
The loopback address (::1) is used to test the TCP/IP stack on a host, similar to 127.0.0.1 in IPv4. An unspecified address (::) indicates that an interface does not have an IPv6 address.
IPv6 hosts can obtain addresses dynamically through three methods, without always requiring a DHCP server.
SLAAC allows a host to generate its own IPv6 address. The router sends router advertisements (RA) every 200 seconds, providing the network prefix (first 64 bits). The host then generates the remaining 64 bits (interface ID) using EUI-64 or random generation. Router solicitation (RS) is when a host requests advertisement from the router.
In this method, SLAAC provides the IPv6 address, but the host also queries a stateless DHCPv6 server for additional configuration information, such as DNS server addresses. The DHCPv6 server does not keep track of the assigned addresses.
The default gateway address is always obtained from the router, not a DHCP server. When a computer starts, it first generates a link-local address (FE80::) for initial communication.