Types of IPv6 addresses

IPv6 is gaining traction and is starting to be deployed rapidly. Adding fuel to this fire is advancements in AI / ML , AR / VR, financial markets and other technologies. Below is accurate and exhaustive list of different types of IPv6 addresses and its use

1. Global Unicast
   • Globally unique public IPv6 addresses usable over the internet.
   • Here are the Global Unicast IPv6 address assignments
2. Unique local
   • Private IPv6 addresses not usable over the internet (ISP will drop packets)
3. Link local
   • Automatically generated IPv6 address when the network interface is enabled with IPv6 support.
   • Address starts with FE8 and then interface ID is generated using EUI-64
   • Used for communication within a subnet like OSPF LSAs, next hop for static routes and NDP
4. Anycast
   • Any global unicast or unique local IPv6 address can be designated as Anycast address
5. Multicast
   • Address block FF00::/8 used for multicast in IPv6
   • Multicast address scopes
     • Interface-local
     • Link-local
     • Site-local
     • Organization-local
     • Global
6. EUI64
   • EUI = Extended Unique Identifier. This method allows automatic generation of IPv6 address using MAC address
   • EUI-64 is a method of converting a 48bit MAC address into 64 bit interface identifier
     • Divide MAC address at the midpoint — e.g 1234 5678 90AB can be divided in to 123456 | 7890AB
     • Insert FFFE in middle — 1234 56FF FE78 90AB
     • Invert the 7th bit from the most significant side  — 1234 56FF FE78 90AB becomes 1034 56FF FE78 90AB
   • This 64 bit interface identifier is then used as host portion of a /64 IPv6 address by adding it on to the 64 bit network prefix making a 128bit IPv6 address
7. :: (two colons)
   • Same as IPv4 0.0.0.0
8. ::1. (loopback)
   • Same as IPv4 127.0.0.0/8 address range. IPv6 only uses a single address for loopback unlike IPv4