The Destination Address field is 48 bits (6 bytes) long, as follows: (In this manual, the Destination Address is normally expressed as a 12"digit hexadecimal number.)
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7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
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MA | MA | MA | MA | MA | MA | U/L | I/G | ||
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MA | MA | MA | MA | MA | MA | MA | MA |
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MA | MA | MA | MA | MA | MA | MA | MA |
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CA | CA | CA | CA | CA | CA | CA | CA |
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CA | CA | CA | CA | CA | CA | CA | CA |
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CA | CA | CA | CA | CA | CA | CA | CA | Least Significant Byte | |
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MA =Manufacturer's Address bits. Note that the two least significant bits of the most significant byte have the following meanings:
U/L | = | 0 | Globally Administered Address |
| = | 1 | Locally Administered Address |
I/G | = | 0 | Individual node address |
| = | 1 | Group of nodes address |
The U/L (Universal/Local) bit determines whether the address is globally administered, or locally administered. A •globally administered address" implies a universally unique address as administered by the IEEE. When shipped from the factory, each Hewlett"Packard LANIC card contains such an address: a unique Manufacturer's Address (08 00 09 hex) assigned to Hewlett"Packard, and the lower six hex digits assigned by Hewlett"Packard. A •locally administered address" is controlled by the user, and is probably not universally unique.
The I/G bit defines the Destination Address as an individual or group address. An •individual" address is associated with a particular station on the network and implies that a single LANIC card is addressed, whereas a •group" address implies more than one station (or card) is addressed.
A group address in the Destination Address Field refers to a •Multicast" or •Broadcast" address. In addition to its individual address, each LANIC card on the LAN can be configured to accept common addresses shared by subgroups of LANIC cards. Such addresses are referred to as •Multicast" addresses; a node's Multicast Address List allows a node to be tied to several different subgroups for receiving common packets.
A •Broadcast" address is a multicast address that denotes the set of all stations on a LAN. It is predefined by the IEEE to consist of all •1s" in the Destination Address Field. By convention and
2%6 General Information