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MAC Toolkit

Paste a MAC in any format and get all its notations, the OUI and NIC, the I/G and U/L bits explained, the EUI-64 and the IPv6 link-local address. Nothing is sent to any server.

Accepts :, -, Cisco (.) or no separators. That's 12 hex digits (48 bits).

Examples

Generates a locally administered unicast MAC (I/G=0, U/L=1).

redzilla.cl — mac 
 
 
 
 Colon —  
 
 Cisco —  
 
 EUI-64 —  
 
 Link-local —  
 
  
 
 
I/G bit (unicast / group)
 
—
 
—
 
 
 
U/L bit (universal / local)
 
—
 
—
 
 
  
 
Notations
 
 
  
FormatUPPERCASElowercase
   
 
 
 

The manufacturer name (OUI) is not resolved locally: this toolkit does not include
        a vendor database and does not query any external service.

 
 How the EUI-64 and link-local are derived 
 
 1. The U/L bit (second least significant bit) of the
            first octet of the MAC is flipped.

 
 2. The bytes FF FE are inserted between
            the OUI (3 bytes) and the NIC (3 bytes), forming a 64-bit identifier.

 
 3. That interface identifier is prepended with the
            link-local prefix fe80::/64 to obtain the IPv6 address.

 
 
 
 
 
Runs locally in your browser · no sign-up · nothing leaves your browser
  
 
 
How it works
 
The kit takes a MAC address (Ethernet / EUI-48, 48 bits) in any format — colons, hyphens, Cisco dotted notation or the 12 raw hex digits — and normalizes it to every notation in upper and lower case. It also splits the OUI (the first 3 bytes, which identify the manufacturer) from the NIC (the last 3, which identify the device) and explains the two control bits of the first octet: I/G (0 = unicast, 1 = multicast/group) and U/L (0 = universal, vendor-assigned; 1 = locally administered).
It also derives the modified EUI-64 identifier using the standard IPv6 procedure (RFC 4291): it flips the U/L bit of the first octet and inserts the bytes ff:fe between OUI and NIC, then builds the link-local IPv6 address under fe80::/64 from that identifier. It includes a locally administered random MAC generator (I/G = 0, U/L = 1), handy for labs and virtual machines. Everything is processed in the browser, with no databases or external services.
 
 
Example: taking 00:1A:2B:3C:4D:5E apart
 
     
  1. Normalization: 00-1a-2b-3c-4d-5e, 001a.2b3c.4d5e (Cisco) and 001a2b3c4d5e (plain) are all the same address.
  2. OUI 00:1a:2b (manufacturer) and NIC 3c:4d:5e (device); bits I/G = 0 (unicast) and U/L = 0 (universal).
  3. EUI-64: the U/L bit is flipped (00 → 02) and ff:fe is inserted in the middle: 021a:2bff:fe3c:4d5e.
  4. Resulting IPv6 link-local address: fe80::21a:2bff:fe3c:4d5e.
    5.  
 
 
 
 
Frequently asked questions
 
 
 What do the I/G and U/L bits of a MAC address mean? 
They are the two least significant bits of the first octet. The I/G bit distinguishes individual frames (0, unicast) from group frames (1, multicast; the broadcast ff:ff:ff:ff:ff:ff is the extreme case). The U/L bit tells whether the address is universal, burned in by the vendor with its OUI (0), or locally administered (1), like the randomized privacy MACs on phones or the ones on virtual machines.
 
 How is a MAC converted into an IPv6 link-local address? 
Via the modified EUI-64: flip the U/L bit of the first octet, insert the bytes ff:fe between the 3 OUI bytes and the 3 NIC bytes, and prepend the resulting 64-bit identifier with fe80::/64. For example, 00:1a:2b:3c:4d:5e produces fe80::21a:2bff:fe3c:4d5e. Many modern systems no longer use this method and generate random identifiers for privacy (RFC 8981).
 
 What is the difference between the Cisco format and the colon format? 
Only the presentation: the address is identical. The colon format groups one byte at a time (00:1a:2b:3c:4d:5e), the hyphen format is the same with a different separator, and the Cisco format groups two bytes with dots (001a.2b3c.4d5e), which is how it appears in IOS show commands. The kit gives you all four notations ready to copy.
 
 Does this tool identify the MAC vendor? 
It splits out the OUI, which is the vendor field, but it does not resolve the vendor name: that would require a multi-megabyte IEEE database or a call to an external service, and this kit runs 100 % locally. The MAC you paste never leaves your browser, which matters when you work with real equipment inventories.
 
 
 
  
   
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 Disclaimer We take great care to keep every tool accurate and review it thoroughly; even so, we can't guarantee it is free of errors or take responsibility for how the results are used. We recommend double-checking anything critical. 
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