Point-To-Point Bridging - Cisco C3201FESMIC-TP= - 3201 Fast EN Switch Mobile Interface Card Expansion Module Software Configuration Manual

Roles and the Associations of Wireless Devices
The Cisco® Metropolitan Mobile Networks (MMN) access layer is created by wireless outdoor access
points and associated clients. A wireless bridge connects and passes packets between multiple network
segments that use the same communications protocol, such as 802.11. Wireless bridges operate at the
data link layer (Layer 2). In general, a bridge filters and forwards an incoming frame based on the MAC
address of that frame-this function is the same whether it is a wireless or a wired bridge.
When two or more bridges in a Cisco MMN are used, one bridge must be defined as the root bridge.
Cisco wireless bridges default to operation in root bridge mode. In any bridge domain (group of
connected bridges) there should exist only one root bridge. Other bridges must be configured to operate
in non-root mode. At time of activation, non-root bridges initiate a link to the root bridge; all bridges can
subsequently transmit data. Clients can only associate to a non-root bridge when that bridge has a
connection to a root bridge. If the connection to a root bridge is severed, all client associations to the
non-root bridge will be terminated.
A workgroup bridge links wired devices to the network through its association with a wireless root
device, either a root access point or a root bridge.
Additional information can be found in the Cisco Metropolitan Mobile Networks 802.11 RF Design and
Deployment white paper at:
http://www.cisco.com/en/US/netsol/ns473/networking_solutions_white_paper0900aecd801016cf.shtml
The station-role root bridge mode accepts associations with non-root bridge devices and can be set to
accept wireless clients. For example:
wd(config)#interface dot11radio interfacenumber
wd(config-in)#station-role root bridge wireless-clients
The root parameter specifies that the bridge operates as a root bridge to which non-root bridges can
associate. The non-root parameter specifies that the router operates as a non-root bridge and must
associate to a root bridge.
The wireless-clients parameter allows association with a root bridge and wireless clients.
A wireless device in bridge mode can be set to automatically select a root or a non-root role. For
example:
wd(config)#interface dot11radio interfacenumber
wd(config-in)#station-role install automatic
If the install parameter is set, the bridge listens for another bridge. If it does not recognize another
bridge, that bridge becomes a root bridge. If it recognizes another bridge, it becomes a non-root bridge
associated to the discovered bridge. If 2 or more wireless bridges are brought up at the same time and
the install parameter is set, the bridge with the lowest MAC address is identified as the root bridge.

Point-to-Point Bridging

In a point-to-point bridging configuration, a non-root bridge associates to a root bridge. Wireless bridges
can be deployed to establish a direct link between two sites. The network traffic between the sites is
bridged, as if it were one network. In this configuration, the bridges emulate a wired point-to-point link.
Point-to-point bridges can be used to link a hot spot to the distribution/aggregation devices in a network
when a wireless connection is more feasible than a wired link.
Point-to-Point Bridging Without Wireless Clients
Figure 2
high-gain antennas and without wireless clients to bridge long distance and maintain high-bandwidth
availability.
shows bridges in a point-to-point configuration. In this scenario, the bridges are deployed with
Understanding Wireless Device Network Roles
Roles and the Associations of Wireless Devices
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