Cisco Cisco Aironet 340 Ethernet Bridges トラブルシューティングガイド
Sub−Optimal/Incorrect Data Rate Settings on the Wireless Bridges
Wireless bridges can run into connectivity issues if you configure the bridges with sub−optimal or incorrect
data rate settings. If you configure the data rates incorrectly on wireless bridges, the bridges fail to
communicate. A typical example is a scenario where one of the bridges is configured for a fixed data rate, for
example, 11 Mbps, and the other bridge is configured with a data rate of 5 Mbps.
data rate settings. If you configure the data rates incorrectly on wireless bridges, the bridges fail to
communicate. A typical example is a scenario where one of the bridges is configured for a fixed data rate, for
example, 11 Mbps, and the other bridge is configured with a data rate of 5 Mbps.
Normally, the bridge always attempts to transmit at the highest data rate set to basic, also called "require", on
the browser−based interface. In case of obstacles or interference, the bridge steps down to the highest rate that
allows data transmission. If one of the two bridges has a data rate of 11 Mbps set, and the other is set to "use
any rate", the two units communicate at 11 Mbps. However, in case of some impairment in the
communication that requires the units to fall back to a lower data rate, the unit set for 11 Mbps cannot fall
back, and communications fail. This is one of the most common problems that relate to data rates. The
workaround is to use optimized data rate settings on the two wireless bridges.
the browser−based interface. In case of obstacles or interference, the bridge steps down to the highest rate that
allows data transmission. If one of the two bridges has a data rate of 11 Mbps set, and the other is set to "use
any rate", the two units communicate at 11 Mbps. However, in case of some impairment in the
communication that requires the units to fall back to a lower data rate, the unit set for 11 Mbps cannot fall
back, and communications fail. This is one of the most common problems that relate to data rates. The
workaround is to use optimized data rate settings on the two wireless bridges.
You can use the data rate settings to set up the bridge to operate at specific data rates. For example, in order to
configure the bridge to operate at 54 Mbps service only, set the 54 Mbps rate to basic, and set the other data
rates to enabled. In order to set up the bridge to operate at 24, 48, and 54 Mbps, set 24, 48, and 54 to basic,
and set the rest of the data rates to enabled. You can also configure the bridge to set the data rates
automatically to optimize either range or throughput. When you enter a range for the data rate setting, the
bridge sets the 6 Mbps rate to basic and the other rates to enabled. When you enter throughput for the data rate
setting, the bridge sets all data rates to basic. Refer to Configuring Radio Data Rates for more information on
how to optimize the data rate settings.
configure the bridge to operate at 54 Mbps service only, set the 54 Mbps rate to basic, and set the other data
rates to enabled. In order to set up the bridge to operate at 24, 48, and 54 Mbps, set 24, 48, and 54 to basic,
and set the rest of the data rates to enabled. You can also configure the bridge to set the data rates
automatically to optimize either range or throughput. When you enter a range for the data rate setting, the
bridge sets the 6 Mbps rate to basic and the other rates to enabled. When you enter throughput for the data rate
setting, the bridge sets all data rates to basic. Refer to Configuring Radio Data Rates for more information on
how to optimize the data rate settings.
Fresnel Zones and Line of Sight Issues
Line of Sight (LoS) is an apparent (invisible) straight line between the transmitter and receiver. In the case of
wireless bridges, the LoS is between the two antennas that connect the bridges, for example a root bridge and
a non−root bridge. The RF LoS is an apparent straight line because RF waves are subject to changes in
direction due to various factors that include refraction, reflection, and diffraction. The problem is that Fresnel
Zones can affect RF LoS. In such a scenario, the connectivity between the bridges can be intermittent, and in
some cases, can lead to complete loss of connectivity between the bridges.
wireless bridges, the LoS is between the two antennas that connect the bridges, for example a root bridge and
a non−root bridge. The RF LoS is an apparent straight line because RF waves are subject to changes in
direction due to various factors that include refraction, reflection, and diffraction. The problem is that Fresnel
Zones can affect RF LoS. In such a scenario, the connectivity between the bridges can be intermittent, and in
some cases, can lead to complete loss of connectivity between the bridges.
The Fresnel Zone is an elliptical area immediately surrounding the visual path. The Fresnel Zone varies
depending on the length of the signal path and the frequency of the signal. A clear line of sight, with Fresnel
Zone margin, indicates that the path has no obstructions that can affect the signal. Fresnel Zones are
depending on the length of the signal path and the frequency of the signal. A clear line of sight, with Fresnel
Zone margin, indicates that the path has no obstructions that can affect the signal. Fresnel Zones are