1

Simple enough, question is in the title. Was trying to find an official document or RFC which designated (or reserved) ffff.ffff.ffff as the Ethernet Broadcast MAC address.

3

Eddie is correct, but I think the IEEE 802.3 standard predates the RFC. Unfortunately I can only get the current 802.3 standard, although his answer is a valid answer, regardless of the timing. It is also defined in the 802.3 standard:

All 1’s in the Destination Address field shall be predefined to be the Broadcast Address. This group shall be predefined for each communication medium to consist of all stations actively connected to that medium; it shall be used to broadcast to all the active stations on that medium. All stations shall be able to recognize the Broadcast Address. It is not necessary that a station be capable of generating the Broadcast Address.

Technically, any MAC address with a 1 in the I/G bit is a broadcast address, even multicast addresses, which must have that bit set to show it is a group address:

The first bit (LSB) shall be used in the Destination Address field as an address type designation bit to identify the Destination Address either as an individual or as a group address. If this bit is 0, it shall indicate that the address field contains an individual address. If this bit is 1, it shall indicate that the address field contains a group address that identifies none, one or more, or all of the stations connected to the LAN. In the Source Address field, the first bit is reserved and set to 0.

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  • That works. Better someone get some points from the green check mark than no one ;). Plus I won't have to wait two days to mark it. Thanks Ron. – Eddie Jan 23 '16 at 3:20
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    Since I voted your answer up, too, we both got something out of it. :) – Ron Maupin Jan 23 '16 at 3:24
3

Figures. I found it minutes after posting. Was looking in the IANA reservations, didn't think to look up the Ethernet RFC specification:

RFC 894

Broadcast Address

The broadcast Internet address (the address on that network with a host part of all binary ones) should be mapped to the broadcast Ethernet address (of all binary ones, FF-FF-FF-FF-FF-FF hex).

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3

The Ethernet broadcast address with all bits as 1 was first officially defined in the original IEEE 802.3 standard Clause 3.2.3.1, published in 1983:

Broadcast Address. A distinguished, predefined multicast address that always denotes the set of all stations on a given LAN.

All 1’s in the Destination Address field shall be predefined to be the Broadcast Address. This group shall be predefined for each communication medium to consist of all stations actively connected to that medium; it shall be used to broadcast to all the active stations on that medium. All stations shall be able to recognize the Broadcast Address. It is not necessary that a station be capable of generating the Broadcast Address.

It was previously defined in the "DIX" standard (1982) as an industry standard.

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