14 Hex Characters in a MAC Address?

I've noticed that a few of the devices I have on my network have fourteen character MAC addresses. As the material I studied said that all MAC addresses were twelve hexadecimal characters, I'm curious to know the hows, whys, and thererfores.

But I've not found anything online about that as yet.

Anyone have any links to information about this?



Reply to
Fred Atkinson
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Could you give an example of such a one, along with an indication of the context in which you found it? For example, did you see one of these pop up in a wireshark trace, or is it something being reported on a device's configuration page (in which case it might be wrong/lying/misleading), or does a device give you

7 fields for editting its MAC address, or ??
Reply to
Walter Roberson

Some DHCP servers tack an extra field on making it look as if there is a 14 char mac address. It is not. I have seen this in Microsoft DHCP server "leases" view and of course the cisco router dhcp server can (must?) be configured with this additional field too.

e.g. ip dhcp pool 3 host client-identifier 0100.166f.0370.02

The 01 at the beginning is the extra bit. Never understood what it was for exactly.

Reply to

From Cisco docs:

'01 represents the Ethernet media type. For a list of media type codes, refer to the "Address Resolution Protocol Parameters" section of RFC

1700, Assigned Numbers.'
Reply to
Slawomir Kawala


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