Understanding Bridge Topologies
Two types of
bridge topology are normally deployed. A large number of the systems are point to point, connecting just
two locations together. Figure 14-1 shows
a typical bridge topology for point-to-point systems.
An increasing number of multipoint systems are being
installed today. In most systems, one bridge is usually defined as the central,
or master, bridge. This provides the central point of data flow from the remote
sites. (See Figure 14-2.)
In some cases, the bridges might also act as an AP permitting
individual wireless clients to associate to the bridge.
The number of possible remote sites is based on the vendor, but
the actual limitation should be addressed by the overall bandwidth needed by
each end user. The central or master bridge is the limiting point. In some
cases, it is desirable to have multiple master bridges, operating on separate,
nonoverlapping frequencies, as shown in Figure 14-3.
Most bridges operate on a Layer 2 level (MAC layer). If the
networks that are being tied together are on different subnets, some type of
router must be installed in at least one site to separate the segments and route
traffic properly. Many installations use routers at every site, permitting not
just segmentation, but also the use of virtual private
network (VPN) tunnels over the RF links for a more secure system. This
can also permit some types of traffic filtering to improve the throughput of the
wireless link.
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