Wireless Bridges

A wireless bridge provides connectivity between two wired LAN segments, and is used
in point-to-point or point-to-multipoint configurations. A wireless bridge is a half-duplex device capable of layer 2 wireless connectivity only. The above figure shows an example of a wireless bridge, while the following figure illustrates where a wireless bridge is used on a wireless LAN.


Wireless Bridge Modes
Wireless bridges communicate with other wireless bridges in one of four modes:

Root Mode
Non-root Mode
Access Point Mode
Repeater Mode

Root Mode
One bridge in each group of bridges must be set as the root bridge. A root bridge can
only communicate with non-root bridges and other client devices and cannot associate
with another root bridge. The above figure illustrates a root bridge communicating with nonroot bridges.

Non-root Mode
Wireless bridges in non-root mode attach, wirelessly, to wireless bridges that are in root mode. Some manufacturers’ wireless bridges support client connectivity to non-root
mode bridges while in bridging mode. This mode is actually a special mode where the
bridge is acting as both an access point and as a bridge simultaneously. When using the
Spanning Tree Protocol, all non-root bridges must have connectivity to the root bridge.

Access Point Mode
Some manufacturers give the administrator the ability to have clients connect to bridges, which is actually just giving the bridge access point functionality. In many cases, the bridge has an “access point” mode that converts the bridge into an access point.

Repeater Mode
Wireless bridges can also be configured as repeaters, as shown in the above figure. In repeater configuration, a bridge will be positioned between two other bridges for the purpose of extending the length of the wireless bridged segment. While using a wireless bridge in this configuration has the advantage of extending the link, it has the disadvantage of decreased throughput due to having to repeat all frames using the same half duplex radio. Repeater bridges are non-root bridges, and many times the wired port will be disabled while the bridge is in repeater mode.


Common Options
The hardware and software options of a wireless bridge are similar to those of an access
point, and for many of the same purposes:

Fixed or Detachable Antennas
Advanced Filtering Capabilities
Removable (Modular) Radio Cards
Variable Output Power
Varied Types of Wired Connectivity