IPv6 Link local address format

[chinpohpang851]

My PC IPv6 local link address is fe80::f420:17f3:0c56:231e  and MAC is 18:03:73:25:e5:cf.

I know for global unicast address using EUI-64 format to get the interface ID, so I wonder how is it for local link address to get its interface ID? 

[Marcin Latosiewicz]

Is the OS using CGA? 

https://en.wikipedia.org/wiki/Cryptographically_Generated_Address

[chinpohpang851]

you mean my pc operating system?

[Masoud Pourshabanian]

Hello,

It can be random.

"The 64-bit interface identifier is either automatically generated from the interface's MAC address using the modified EUI-64 format, obtained from a DHCPv6 server, automatically established randomly, or assigned manually."

https://en.wikipedia.org/wiki/IPv6_address

[Masoud Pourshabanian]

Adding to my previous comment,

"Computers running Windows Vista® or Windows Server® 2008 by default generate random interface IDs for non-temporary autoconfigured IPv6 addresses, including public and link-local addresses, rather than EUI-64-based interface IDs. A public IPv6 address is a global address that is registered in DNS and is typically used by server applications for incoming connections, such as a Web server. You can disable this default behavior with the command

netsh interface ipv6 set global randomize­identifiers=disabled 

When disabled, IPv6 uses EUI-64-based interface IDs.

https://technet.microsoft.com/en-us/magazine/2007.08.cableguy.aspx

Hope it helps,

Masoud