How to use the mac address to ipv6 converter
- Select MAC to IPv6 or IPv6 to MAC from the direction dropdown.
- Enter your MAC address (for example
00:1A:2B:3C:4D:5E) or an IPv6 link-local address. - The tool instantly computes the EUI-64 interface identifier and the full link-local address.
- Copy the result for use in network configuration, firewall rules or documentation.
How the EUI-64 calculator works
The EUI-64 calculator transforms a 48-bit MAC address into a 64-bit IPv6 interface identifier through three steps defined in RFC 4291.
- Split the MAC into two 24-bit halves. For
00:1A:2B:3C:4D:5E, the halves are00:1A:2Band3C:4D:5E. - Insert the 16-bit value
FF:FEbetween them, producing00:1A:2B:FF:FE:3C:4D:5E. - Flip the seventh bit of the first byte (the universal/local bit). The first byte
00(binary00000000) becomes02(binary00000010).
The final EUI-64 identifier is 021a:2bff:fe3c:4d5e. Prepending the link-local prefix fe80::/10 gives the complete mac to ipv6 link local address: fe80::21a:2bff:fe3c:4d5e.
Common MAC to IPv6 conversions
This table shows several typical results from the mac address to ipv6 converter so you can verify your own calculations.
| MAC address | EUI-64 identifier | Link-local IPv6 |
|---|---|---|
00:00:00:00:00:00 | 0200:00ff:fe00:0000 | fe80::200:ff:fe00:0 |
00:1A:2B:3C:4D:5E | 021a:2bff:fe3c:4d5e | fe80::21a:2bff:fe3c:4d5e |
AA:BB:CC:DD:EE:FF | a8bb:ccff:fedd:eeff | fe80::a8bb:ccff:fedd:eeff |
FF:FF:FF:FF:FF:FF | fdff:ffff:feff:ffff | fe80::fdff:ffff:feff:ffff |
Note how AA (binary 10101010) becomes A8 (binary 10101000) after the U/L bit flip, because the second least-significant bit changes from 1 to 0.
Reversing IPv6 back to a MAC address
To go from a mac to ipv6 link local address back to the original hardware address, the process is reversed. Take the last 64 bits of the IPv6 address, remove the inserted ff:fe from the middle and flip the U/L bit again.
For example, given fe80::21a:2bff:fe3c:4d5e:
- Expand to full form:
021a:2bff:fe3c:4d5e. - Remove bytes 4 and 5 (
ff:fe):02:1a:2b:3c:4d:5e. - Flip bit 7 of the first byte:
02XOR02=00. - Result:
00:1a:2b:3c:4d:5e.
If the middle bytes are not ff:fe, the address was not formed by standard EUI-64 and cannot be reliably reversed to a MAC.
Why the U/L bit matters
The seventh bit of the first octet is the universal/local (U/L) bit. When set to 0, the address is universally administered (assigned by IEEE to a manufacturer). When set to 1, it is locally administered (configured manually or by software).
RFC 4291 requires flipping this bit during EUI-64 conversion so that universally assigned MACs produce interface identifiers with the U/L bit set to 1, distinguishing them from locally assigned ones. This is why every mac address to ipv6 converter must perform the XOR operation on the first byte; skipping it produces an invalid link-local address that will not match what operating systems generate.
Practical uses for EUI-64 addresses
Network engineers use the EUI-64 calculator when configuring IPv6 on routers and switches. Many devices can derive their link-local address from the interface MAC using this exact algorithm. Knowing the resulting address helps with:
- Writing firewall rules that reference specific hosts on a local segment.
- Troubleshooting neighbor discovery failures when a device does not respond to pings.
- Documenting network topology without logging into each device individually.
- Verifying that privacy extensions (RFC 4941) are disabled when stable addresses are required.
You can also use tools like the mac address converter to reformat MAC addresses before feeding them into this converter, or the ipv6 subnet mask calculator to plan subnets around these link-local addresses.
Worked examples
| Example | Input | Result |
|---|---|---|
| Standard MAC to link-local | Direction: mac-to-ipv6; Input address: 00:1A:2B:3C:4D:5E | EUI-64 identifier: 021a:2bff:fe3c:4d5e; Link-local address: fe80::21a:2bff:fe3c:4d5e; U/L bit in the MAC: 0 (universally administered) |
| Broadcast MAC | Direction: mac-to-ipv6; Input address: FF:FF:FF:FF:FF:FF | EUI-64 identifier: fdff:ffff:feff:ffff; Link-local address: fe80::fdff:ffff:feff:ffff; U/L bit in the MAC: 1 (locally administered) |
| Reverse: IPv6 to MAC | Direction: ipv6-to-mac; Input address: fe80::21a:2bff:fe3c:4d5e | MAC address: 00:1a:2b:3c:4d:5e; EUI-64 identifier: 021a:2bff:fe3c:4d5e |
| Locally administered MAC | Direction: mac-to-ipv6; Input address: 02:00:00:00:00:01 | EUI-64 identifier: 0000:00ff:fe00:0001; Link-local address: fe80::ff:fe00:1; U/L bit in the MAC: 1 (locally administered) |
FAQ
What is a mac address to ipv6 converter?
It is a tool that applies the EUI-64 algorithm to transform a 48-bit Ethernet MAC address into a 64-bit IPv6 interface identifier, then prepends the fe80:: prefix to produce a link-local address.
How do I convert a mac to ipv6 link local address manually?
Split the MAC in half, insert FF:FE between the halves, flip the seventh bit of the first byte, format as four hex groups separated by colons, and prepend fe80::.
Why is FFFE inserted in the middle?
FF:FE is reserved by IEEE specifically for EUI-64 conversion. Its presence signals that the 64-bit identifier was derived from a 48-bit MAC rather than being a native EUI-64 hardware address.
Can I reverse any IPv6 address back to a MAC?
Only if the address was generated via EUI-64. You can check by looking for ff:fe in the middle of the interface identifier. Addresses created by privacy extensions or manual assignment cannot be reversed.
Does this EUI-64 calculator work with dash-separated MACs?
Yes. The tool accepts colons, hyphens, dots and plain hex strings. It normalizes the input before performing the conversion.
Is the link-local prefix always fe80::?
Yes. Per RFC 4291, all IPv6 link-local unicast addresses use the fe80::/10 prefix. The remaining 54 bits of the first 64-bit block are zeros, so the prefix is written as fe80::.