IPv6 Unicast Address

Let’s talk about IPv6 Unicast address.

There are mainly 4 types of unicast addresses.

                Global Unicast

                Link-local Unicast

                Site-local / Unique-local Unicast

                Special Addresses

Global Unicast:

Global unicast addresses are global addresses i.e. public IP addresses. They are globally unique. It starts with binary prefix 001 which is 2 in decimal. So global unicast addresses starts with 2000::/3.

They are globally routable and reachable in Internet. IANA assigns a /12 addresses to five regional internet registries i.e. APNIC, AFRINIC, RIPE, ARIN and LACNIC. They are giving a /32 address for each service provider and a /48 for each Enterprise.

Keep in mind that not less than or equal to /64 addresses are routable in internet. Even it is suggested not to route any address less than or equal to /48 (preferably /32) in internet to keep global routing table small.

I think no more explanation is needed for Global Unicast. It’s just public IP address. We all know what the purposes of public IP are.

Link-Local Unicast:

It’s like private IP of IPv4 but it’s a mandatory IP for all interfaces running IPv6. i. e. all the interface running IPv6 must have a link-local unicast address. Pretty interesting huh!!!

This IP address used to communicate with local hosts, neighbor discovery and routing protocol updates. It’s assigned automatically. It always starts with FE80. So a link local address could be FE80::/64 though the reserved block is FE80::/10.

Routers don’t forward any packets with link-local addresses.

Site-local / Unique-local unicast address:

This kind of address is used in local sites. It’s also a kind of private IP address.  So the routers will not forward site local address packets in internet. It’s not automatically created in an interface like link-local address; it should be assigned if needed. It is generally used for site to site communication among a company / enterprise.

Interesting information of unique-local address is it is globally unique but used only in sites or limited area. So any sites combined / merged with one another, there will not be any issue like conflict / duplicate address.  Re-numbering will not be required for it.

The prefix for unique-local address is FC00::/7

Special Addresses:

There are several IPv6 special addresses.

Loopback address is        ::1/128

Unspecified address is   ::/128

IPv4-Mapped address   ::FFFF:0:0/96 (Not routable in internet)

IPv4-compitable address              ::<ipv4-address>/96 (Not routable in internet)

 I have tried to give a concept about the types of IPv6 Unicast. For details information you can take help from google.