For example, beginning with Windows Vista, Windows uses a randomly generated Interface ID instead of one created with EUI-64. Due to these concerns, a randomly generated Interface ID may be used instead.ĭepending upon the operating system, a device may use a randomly generated Interface ID instead of using the MAC address and the EUI-64 process. They are concerned that their packets can be traced to the actual physical computer. However, this has caused privacy concerns among many users. It also allows network administrators to easily track an IPv6 address to an end-device using the unique MAC address. The advantage of EUI-64 is the Ethernet MAC address can be used to determine the Interface ID. Note: The use of the U/L bit and the reasons for reversing its value are discussed in RFC 5342. The result is an EUI-64 generated Interface ID of FE99:47FF:FE75:CEE0. In this example the 0 in bit 7 is changed to a 1.

Step 3: Convert the first 2 hexadecimal values of the OUI to binary and flip the U/L bit (bit 7). Step 2: Insert the hexadecimal value FFFE, which in binary is: 1111 1111 1111 1110. Step 1: Divide the MAC address between the OUI and device identifier. The EUI-64 process is illustrated in Figure 1, using R1’s GigabitEthernet MAC address of FC99:4775:CEE0. 24-bit Device Identifier from the client MAC address.The inserted 16-bit value FFFE (in hexadecimal).This means that if the 7th bit is a 0 it becomes a 1, and vice versa. 24-bit OUI from the client MAC address, but the 7th bit (the Universally/Locally (U/L) bit) is reversed.Device Identifier – The device identifier is a unique 24-bit (6 hexadecimal digits) value within a common OUI.Īn EUI-64 Interface ID is represented in binary and is made up of three parts:.Organizationally Unique Identifier (OUI) – The OUI is a 24-bit (6 hexadecimal digits) vendor code assigned by IEEE.This process uses a client’s 48-bit Ethernet MAC address, and inserts another 16 bits in the middle of the 48-bit MAC address to create a 64-bit Interface ID.Įthernet MAC addresses are usually represented in hexadecimal and are made up of two parts: IEEE defined the Extended Unique Identifier (EUI) or modified EUI-64 process.

Convert mac address to ipv6 address