bridge. The Bridge looks at the source address of each packet generated on the subnetwork and creates a database containing these addresses.

Note: If a node does not generate any packets, its location cannot be dynamically learned by the Bridge Module.

When a packet is received by the Bridge Module, its destination address is compared with the addresses in the source subnetwork database. Table 1-1 describes what happens when a packet is received by the Bridge Module.

Table 1-1. Packet Distribution by Bridge Module

The Destination Address is..

The Packet is...

 

 

Found in the source

Considered to be local to that

subnetwork database

subnetwork (its source and destination

 

are on the same subnetwork). The

 

Bridge Module does not forward the

 

packet.

 

 

Not found in the source

Considered to be on a different

subnetwork database

subnetwork and forwarded onto the

 

other subnetwork (or the destination

 

node has not generated any traffic).

 

 

High-Performance Design

While address filtering can reduce traffic loads on your network, it is important to overall network integrity for a learning bridge to run as fast as the network. The Bridge Module ensures high performance in the following ways:

1.It uses high-speed multi-port memory so the IEEE 802.3 controllers and the CPU all have separate access to the common packet memory. Once a packet is received into this memory, it does not have to be copied to be forwarded.

1 - 6 ONline Ethernet Bridge Module Installation and Operation Guide

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3Com 5102B-EE High-Performance Design, Packet Distribution by Bridge Module, Destination Address is Packet is