Bridges
A bridge connects two physical network segments that
use the same protocol. Each network bridge builds a
MAC address table of all devices that are connected on
its ports. When packet traffic arrives at the bridge and its
target address is local to that side of the bridge, the
bridge filters that frame, so it stays on the local side of
the bridge.
If the bridge is unable to find the target address on the
side that received the traffic, it forwards the frame across
the bridge, hoping the destination will be on the other
network segment. In some cases, multiple bridges are
cascaded.
Figure 17-7 shows how a bridge connects two LAN segments.Figure 17-7 Using a Bridge to Connect Two LAN
Segments
Switches
You can think of a switch as an “intelligent” hub. A
switch does what a hub does—but more efficiently and
intelligently. It analyzes the traffic as it flows. A switch
builds a port-to-MAC address table as devices start
communicating. This means a switch offers dramatically
better performance than a hub. To analyze the traffic,
specialized hardware (called application-specific
integrated circuits [ASICs]) is needed. If we replace the