convert mac address to ipv6 unique local unicast

The reason for inverting can be found in RFC4291 section 2.5.1. Therefore, when the bit is inverted, it maintains its original scope (global unique address is still global unique and vice versa). It is worth noticing that in the OUI portion, the globally unique addresses assigned by the IEEE has always been set to 0 whereas the locally created addresses has 1 configured. If 0, the address is locally administered and if 1, the address is globally unique. This bit identifies whether this interface identifier is universally or locally administered. Next, the seventh bit from the left, or the universal/local (U/L) bit, needs to be inverted. Here is an example showing how a the MAC Address is used to generate EUI. IEEE has chosen FFFE as a reserved value which can only appear in EUI-64 generated from the an EUI-48 MAC address. The 16-bit 0xFFFE is then inserted between these two 24-bits for the 64-bit EUI address.

The MAC address is first separated into two 24-bits, with one being OUI (Organizationally Unique Identifier) and the other being NIC specific. The IPv6 EUI-64 format address is obtained through the 48-bit MAC address. This feature is a key benefit over IPv4 as it eliminates the need of manual configuration or DHCP as in the world of IPv4. Extended Unique Identifier (EUI), as per RFC2373, allows a host to assign iteslf a unique 64-Bit IP Version 6 interface identifier (EUI-64).

Convert mac address to ipv6 unique local unicast