MAC to IPv6 converter — EUI-64, link-local and global
Type a MAC address to get its modified EUI-64 interface ID and fe80:: link-local address. Add your /64 prefix for the global SLAAC address. Or paste an IPv6 address to get the MAC back. Results update as you type.
Reverse: IPv6 address to MAC
How a MAC address becomes an IPv6 address
Three steps, defined in RFC 4291. Here they are for 00:1A:2B:3C:4D:5E.
2. Insert FF:FE 00:1A:2B:FF:FE:3C:4D:5E
3. Flip bit 7 (U/L) 02:1A:2B:FF:FE:3C:4D:5E
→ Interface ID 021a:2bff:fe3c:4d5e
→ Link-local fe80::21a:2bff:fe3c:4d5e
→ Global (2001:db8:abcd:12::/64) 2001:db8:abcd:12:21a:2bff:fe3c:4d5e
Link-local vs global
Every IPv6 interface has a link-local address in fe80::/64. It only works on the local network segment (routers never forward it) and is used for neighbour discovery and router advertisements. A global address uses the /64 prefix your router advertises; with SLAAC the device appends the same EUI-64 interface ID to it, so the last 64 bits match the link-local address.
Why many devices no longer do this
An EUI-64 address carries the MAC, so the same laptop could be recognised on every network it joins. Windows, macOS, iOS and Android now build global addresses from random (RFC 4941 temporary) or hashed (RFC 7217 stable-privacy) interface IDs. Routers, switches, servers and embedded devices still commonly use EUI-64, which is why network engineers need this conversion when reading neighbour tables, ACLs or logs.
Cisco and Linux
On Cisco IOS, ipv6 address 2001:db8:abcd:12::/64 eui-64 builds the global address exactly as above. On Linux, sysctl net.ipv6.conf.eth0.addr_gen_mode=0 selects EUI-64, and ip -6 addr shows the result. To find which company made the card, put the MAC into our MAC address lookup.
Frequently asked questions
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How is an IPv6 address made from a MAC address?
With modified EUI-64 (RFC 4291). Split the 48-bit MAC in half, insert FF:FE in the middle to make 64 bits, and flip the seventh bit of the first byte (the universal/local bit). 00:1A:2B:3C:4D:5E becomes 02:1A:2B:FF:FE:3C:4D:5E, written as the interface ID 21a:2bff:fe3c:4d5e. Put fe80:: in front for the link-local address, or your network's /64 prefix for the global one.
What is the IPv6 link-local address for 00:1A:2B:3C:4D:5E?
fe80::21a:2bff:fe3c:4d5e. The first byte 00 becomes 02 because the universal/local bit is flipped, and ff:fe is inserted between 2b and 3c.
Why is the seventh bit flipped?
In a MAC address that bit is 0 for a factory (universal) address. IPv6 inverts it so that hand-typed interface IDs such as ::1 or ::2 count as "local" without anyone having to set the bit. It is the most common mistake when people convert by hand: 00 becomes 02, 02 becomes 00, A4 becomes A6.
Can I get the MAC address back from an IPv6 address?
Only if the address was built with EUI-64, which you can tell from FF:FE in the middle of the last 64 bits. Paste it into the reverse box and the tool removes FF:FE and flips the bit back. Most phones and PCs today use random temporary addresses (RFC 4941) or "stable privacy" addresses (RFC 7217) instead, and those cannot be turned back into a MAC.
Do Windows, Android and iPhone still use EUI-64?
Mostly not for global addresses: Windows, macOS, iOS and Android generate random interface IDs by default to stop tracking. EUI-64 is still common on routers, switches, Linux servers, Cisco IOS interfaces (ipv6 address 2001:db8::/64 eui-64), IoT devices and for link-local addresses on many systems.
What prefix should I enter for the global address?
The /64 your ISP or router hands to that network, for example 2001:db8:abcd:12::/64. On Linux run ip -6 addr, on Windows ipconfig, and take the first four groups of any global address. SLAAC only works with a /64, so the tool rejects other lengths.
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