AC206-DS04-R View Datasheet(PDF) - Broadcom Corporation
Part Name
Description
MFG CO.
'AC206-DS04-R' PDF : 70 Pages View PDF
Preliminary Data Sheet
07/08/02
AC206
ADDRESSING ALGORITHM, ROUTING, LEARNING AND AGING
ADDRESS TABLE
The address table can store up to 1K entries and each entry consists of 48-bit MAC address, 8-bit port identifier, 1-bit
indication flag and 6-bit aging timer.
Table 2: Content of Address Lookup Table
3130
V
Timer
Port#
MAC#3
MAC#4
Bit 30: Entry valid/empty indication, 1 = valid entry, 0 = empty entry.
Bit 29-24: Aging timer.
Bit 23-16: Port number
MAC#1
MAC#5
0
MAC#2
MAC#6
ADDRESS RECOGNITION
The exclusive or addressing algorithm is used for address lookup table addressing (see the following figure).
MAC#6 xor MAC#4 xor MAC#2
=
MAC#5 xor MAC#3 xor MAC#1
=
Hashed address[15:0]
Figure 2: Exclusive or Hashing Algorithm
The final address of address lookup table is the hashed address[9:0].
ROUTING DECISION
If a record is empty, the packet is broadcast and treated as an unknown frame. Otherwise, the record is read, and compared
with the current DA. If two addresses are the same, the port number is decided, and the packet is forwarded to the assigned
port. If address collision occurred, different MAC address, the incoming packet is considered an unknown packet.
Document AC206-DS05-405-R
Broadcom
Addressing Algorithm, Routing, Learning and Aging
Page 9
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