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RFC1700 - часть 131

0 23 47

| | |

0000 0001 0000 0000 0101 1110 0xxx xxxx xxxx xxxx xxxx xxxx

Multicast Bit 0 = Internet Multicast

Reynolds & Postel [Page 172]

RFC 1700 Assigned Numbers October 1994

1 = Assigned by IANA for other uses

The latter representation corresponds to the Internet standard

bit-order, and is the format that most programmers have to deal with.

Using this representation, the range of Internet Multicast addresses


01-00-5E-00-00-00 to 01-00-5E-7F-FF-FF in hex, or to in dotted decimal


Ethernet hardware addresses are 48 bits, expressed as 12 hexadecimal

digits (0-9, plus A-F, capitalized). These 12 hex digits consist of

the first/left 6 digits (which should match the vendor of the Ethernet

interface within the station) and the last/right 6 digits which

specify the interface serial number for that interface vendor.

Ethernet addresses might be written unhyphenated (e.g., 123456789ABC),

or with one hyphen (e.g., 123456-789ABC), but should be written

hyphenated by octets (e.g., 12-34-56-78-9A-BC).

These addresses are physical station addresses, not multicast nor

broadcast, so the second hex digit (reading from the left) will be

even, not odd.

At present, it is not clear how the IEEE assigns Ethernet block

addresses. Whether in blocks of 2**24 or 2**25, and whether

multicasts are assigned with that block or separately. A portion of

the vendor block address is reportedly assigned serially, with the

other portion intentionally assigned randomly. If there is a global

algorithm for which addresses are designated to be physical (in a

chipset) versus logical (assigned in software), or globally-assigned

versus locally-assigned addresses, some of the known addresses do not

follow the scheme (e.g., AA0003; 02xxxx).

00000C Cisco

00000E Fujitsu

00000F NeXT

000010 Sytek

00001D Cabletron

000020 DIAB (Data Intdustrier AB)

000022 Visual Technology

00002A TRW

Reynolds & Postel [Page 173]

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