Basically, you take the 48-bit MAC address, split it in half, insert FFFE to extend it to 64 bits, and flip the U/L bit. So - if the bit is already flipped there's no need to flip it again. To calculate the modified EUI-64, refer to RFC 4291, IP Version 6 Addressing Architecture, Appendix A for the algorithm. What about VMs, virtual hosts? To me it looks like they have no other choice but to use a self-assigned MAC i.e. The 7th bit is the U/L - Universal (globally unique, OUI-enforced) i.e. Taking that info and combining it with MAC-addresses in general, the OUI specifically:
Quite simply, this mechanism takes the 48-bit Media Access Control (MAC) address of the interface - which can normally be assumed to be globally unique - and converts it into a 64-bit Interface ID by inserting a reserved 16-bit value of 0xFFFE into the middle of the MAC address and "flipping" the Universal/Local (U/L) bit of the MAC address to 1. On broadcast interfaces (where hosts are most likely to appear), a mechanism called MAC-to-EUI64 conversion is used. The first step in this process is the determination of the 64-bit Interface ID portion of the address. When an IPv6 host first becomes active on a link, it can self-configure its own interface address. Taken from Jeff Doyle's TCP/IP, Volume 1, 2/e (my preferred source) Note: The command to assign an IPv6 EUI-64 format address is Example However, per RFC4291 2.5.1 (The use of the universal/local bit in the Modified EUI-64 format identifier is to allow development of future technology that can take advantage of interface identifiers with universal scope), this may change in the future as the technology evolves. Once the above is done, we have a fully functional EUI-64 format address.Īnother doubt or frequently asked question is, are IPv6 devices (routers etc) today doing anything to that universal/local bit? Currently, nothing is being done be the U/L bit 1 or 0. 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.
Convert mac address into ipv6 eui 64 manual#
This feature is a key benefit over IPv4 as it eliminates the need of manual configuration or DHCP as in the world of IPv4. 13 acronyms in this thread the most compressed thread commented on today has 16 acronyms.Extended Unique Identifier (EUI), as per RFC2373, allows a host to assign iteslf a unique 64-Bit IP Version 6 interface identifier (EUI-64). Substitutes new text for old text in a text stringīeep-boop, I am a helper bot. Returns the rightmost characters from a text value These can be converted to EUI-64 and then to modified EUI-64 form for creating an IPv6. Returns a specific number of characters from a text string starting at the position you specify Of course, most devices still use the older 48-bit MAC address format. Returns the leftmost characters from a text value Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: Fewer LettersĢ019+: Combines the text from multiple ranges and/or strings, but it doesn't provide the delimiter or IgnoreEmpty arguments. Stateless Address Autoconfiguration (SLAAC): Uses EUI-64 (64-bit extended unique identifier) to determine a globally unique address based on the MAC address.
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