Specifications

9-1

Chapter 9

Ethernet Bridge Operation

Bridges are devices that are added to a network to allow expansion beyond the limits of the IEEE

802.3 speciﬁcation. They are also used to connect two similar networks together, allowing

communication between them. Bridges accomplish this by reading in frames and deciding to either

ﬁlter or forward the frame based on the destination address of the frame. The following sections detail

the operation of bridges and their functions.

Filtering and Forwarding

Bridges decide whether to forward or ﬁlter a frame based on the location

of the destination with respect to the source. They dynamically learn the

location of devices by logging the source address of each frame and the

port it was received on in their Source Address Table (SAT). Refer to

Figure 9-1, which shows two Ethernet LANs connected by a bridge, and

the following explanation on the ﬁltering and forwarding process.

Figure 9-1. Use of Ethernet Bridges

ST-500 with Lanview

Network 1

Network 2

Station A

Station B

Station C

Station D

BRIDGE

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