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Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
Troubleshooting
0(120) *5620(124) *5640(128) *5660(132) *5680(136) *5700(140)
* = May only be selected by Dynamic Frequency Selection (DFS)
Listen Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(6
0) 5320(64) 5500(100) 5520(104) 5540(108) 5560(112) 5580(116) 5660(132) 5680(136
) 5700(140) 5745(149) 5765(153) 5785(157) 5805(161) 5825(165) 4950(20) 4955(21)
4960(22) 4965(23) 4970(24) 4975(25) 4980(26)
Note
An asterisk indicates that this channel has DFS enabled.
Frequency Planning
Use alternate adjacent channels in adjacent sectors. If you have two RAPs deployed at the same location,
you must leave one channel in between.
Weather radars operate within the band 5600 to 5650 MHz, which means that channel 124 and 128 might
be affected, but also channel 120 and 132 might suffer from weather radar activity.
If the mesh access point does detect radar, the controller and the mesh access point both will retain the
channel as the configured channel. The controller retains it in volatile memory associated with the mesh
access point, and the mesh access point has it stored in its flash as configuration. After the 30 minute
quiet period, the controller returns the mesh access point to the static value, regardless of whether the
mesh access point has been configured with a new channel or not. In order to overcome this, configure
the mesh access point with a new channel, and reboot the mesh access point.
Once radar is reliably detected on a channel, that channel, and the two surrounding channels, should be
added to the RRM exclusion list, as follows:
(Cisco Controller) > config advanced 802.11a channel delete <channel>
A mesh access point will go to a new channel as picked by RRM, and it will not consider excluded
channels.
In the case where radar is detected on channel 124, for instance, channels 120, 124, and 128 should be
added to the exclusion list. In addition, do not configure RAPs to operate on those channels.
Good SNRs
For European installations, the minimum recommendation is increased to 20 dB of SNR. The extra dBs
are used to mitigate the effects of radar interference with packet reception, which is not observed in non
DFS environments.
AP Placement
Collocated mesh access points should have a minimum of 10 feet of vertical separation or 100 feet of
horizontal separation.
Check Packet Error Rate
Mesh access points that have an high error rate, greater than 1%, should have mitigation applied to them,
by changing the channels used in the case of noise and interference, by adding additional mesh access
points in the transmission path, moving the mesh access points to different sectors, or by adding
additional mesh access points.