Cisco Cisco Aironet 340 Ethernet Bridges Guia De Resolução De Problemas
background interference level found in a specific environment, for reduced overhead contention with other
wireless systems.
wireless systems.
A CCA threshold can decrease the receiver sensitivity by changing the absolute receive power level above
which the channel is normally considered busy. The default value of the CCA parameter is 75. However, you
can increase the CCA threshold to reduce noise in environments. CCA values can be set independently for
root and non−root bridges.
which the channel is normally considered busy. The default value of the CCA parameter is 75. However, you
can increase the CCA threshold to reduce noise in environments. CCA values can be set independently for
root and non−root bridges.
There might be intermittent connectivity loses with wireless bridges if the CCA value is not configured
correctly. Ensure that the CCA value is not set to zero and is set to the value close to the default value of 75 if
not the default value. Wireless bridges that run Cisco IOS® Software Releases earlier than 12.3(2)JA hit a
bug which changes the default CCA value to zero upon reboot of the device. Refer to Cisco bug ID
CSCed46039 (registered customers only) for more information on this bug and the workaround.
correctly. Ensure that the CCA value is not set to zero and is set to the value close to the default value of 75 if
not the default value. Wireless bridges that run Cisco IOS® Software Releases earlier than 12.3(2)JA hit a
bug which changes the default CCA value to zero upon reboot of the device. Refer to Cisco bug ID
CSCed46039 (registered customers only) for more information on this bug and the workaround.
Other Issues That Degrade the Performance of Wireless Bridges
The materials that the RF signal can penetrate can determine the performance of the wireless bridge. The
density of the materials used in the construction of a building determine the number of walls the RF signal can
pass through and still maintain adequate coverage. Material impact on signal penetration are:
density of the materials used in the construction of a building determine the number of walls the RF signal can
pass through and still maintain adequate coverage. Material impact on signal penetration are:
Paper and vinyl walls have little effect on RF signal penetration.
1.
Solid and pre−cast concrete walls limit signal penetration to one or two walls without degrading
coverage.
coverage.
2.
Concrete and concrete block walls limit signal penetration to three or four walls.
3.
Wood or drywall allows for adequate signal penetration for five or six walls.
4.
A thick metal wall causes signals to reflect off, resulting in poor signal penetration.
5.
Chain link fence and wire mesh with 1 to 1½" spacing act as ½" waves that block a 2.4 GHz signal.
6.
When you deploy a wireless bridge link through a window, the window glass can introduce
significant signal loss. Typical losses range from 5 to 15 dB per window, depending upon the type of
glass. Your deployment plan must take this extra loss into account conservatively when you plan
antenna gains and power settings.
significant signal loss. Typical losses range from 5 to 15 dB per window, depending upon the type of
glass. Your deployment plan must take this extra loss into account conservatively when you plan
antenna gains and power settings.
7.
Disable Concatenation on the bridge. Concatenation is the process where multiple packets are
aggregated into a single packet to increase the throughput. When the bridge connects to a low speed
link on the wired side this poses a problem. Issue this command in order to disable concatenation.
aggregated into a single packet to increase the throughput. When the bridge connects to a low speed
link on the wired side this poses a problem. Issue this command in order to disable concatenation.
bridge(config)#interface dot11radio0
bridge(config−if)#no concatenation.
8.
Wireless bridges can experience intermittent connectivity problems or total loss of connectivity if
there is loose connectivity between the cables that connect the wireless bridges to the power injector
and the antenna. As a first step, check if the cables are connected properly. This especially helps in
cases where the wireless bridges were working previously but suddenly lost connectivity.
there is loose connectivity between the cables that connect the wireless bridges to the power injector
and the antenna. As a first step, check if the cables are connected properly. This especially helps in
cases where the wireless bridges were working previously but suddenly lost connectivity.
9.
CCA is essentially the establishment of a noise floor below which it ignores RF inputs, in search of a
good, solid signal. With the programmable CCA feature, wireless bridges can be configured to a
particular background interference level found in a specific environment, for reduced overhead
contention with other wireless systems. A CCA threshold can decrease the receiver sensitivity by
changing the absolute receive power level above which the channel is normally considered busy. The
default value of the CCA parameter is 75. However, you can increase the CCA threshold to reduce
noise in environments. CCA values can be set independently for root and non−root bridges. There
might be intermittent connectivity loses with wireless bridges if the CCA value is not configured
correctly. Ensure that the CCA value is not set to zero.
good, solid signal. With the programmable CCA feature, wireless bridges can be configured to a
particular background interference level found in a specific environment, for reduced overhead
contention with other wireless systems. A CCA threshold can decrease the receiver sensitivity by
changing the absolute receive power level above which the channel is normally considered busy. The
default value of the CCA parameter is 75. However, you can increase the CCA threshold to reduce
noise in environments. CCA values can be set independently for root and non−root bridges. There
might be intermittent connectivity loses with wireless bridges if the CCA value is not configured
correctly. Ensure that the CCA value is not set to zero.
10.
Before you implement a wireless network, make sure that you understand the behavior of RF waves through
the different materials.
the different materials.