AC206-DS05-405-R datasheet(21/70 Pages) BOARDCOM

21 / 70 page

Preliminary Data Sheet

AC206

07/08/02

B roa dcom

Document

AC206-DS05-405-R

Addressing Algorithm, Routing, Learning and Aging

Page 9

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.

Bit 30: Entry valid/empty indication, 1 = valid entry, 0 = empty entry.

Bit 29-24: Aging timer.

Bit 23-16: Port number

ADDRESS RECOGNITION

The exclusive or addressing algorithm is used for address lookup table addressing (see the following figure).

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.

Table 2: Content of Address Lookup Table

3130

Timer

Port#

MAC#1

MAC#2

MAC#3

MAC#4

MAC#5

MAC#6

MAC#4

MAC#2

xor

Hashed address[15:0]

MAC#5

MAC#3

MAC#1

xor

AC206-DS05-405-R Datasheet(PDF) 21 Page - Broadcom Corporation.