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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
7.
RAP receives the new channel information and sends channel change frames (unicast, encrypted) to
MAPs, and each MAP sends the same information to its lower children down the sector. Each mesh
access point sends the channel change frames once every 100 msecs for a total of five times.
8.
Each mesh access point tunes to the new channel and enters into
silent mode
. During silent mode
only the receiver is ON. There is no packet transmission happening. AP keeps scanning the new
channel for any radar presence for 60 seconds. This is called
channel availability check (CAC)
.
The
MAPs should not disconnect from the controller. The network should remain stable during this one
minute period.
DFS functionality allows a MAP that detects a radar signal to transmit that up to the RAP, which then
acts as if it has experienced radar and moves the sector. This is termed the
coordinated channel change
.
This functionally can be turned on or off on the controller. Coordinated channel change is enabled by
default.
To enable DFS, enter:
(Cisco Controller) >
config mesh full-sector-dfs enable
To verify that DFS is enabled on the network, enter:
(Cisco Controller) > show network
Note
A MAP that detects radar should send a message to the RAP, unless the parent has a different BGN, in
which case it does not send messages for a coordinated sector change. Instead the MAP reenters the
SCAN state and search on non-radar seen channels for a new parent.
Note
Ensure that none of your mesh access points are using DEFAULT BGN.
Note
A repeated radar event on the MAP (radar triggers once, then almost immediately again), will cause the
MAP to disconnect.
Preparation in a DFS Environment
•
To verify that your controller is set to the correct country domain, enter:
(Cisco Controller) >
show country
•
To check mesh access point country and channel setting on controller, enter:
(Cisco Controller)>
show ap config 802.11a
ap name
•
To identify channels available for mesh, enter:
(Cisco Controller)>
show ap config 802.11a
ap name
Look for the allowed channel list.
Allowed Channel List....................... 100,104,108,112,116,120,124,
......................................... 128,132,136,140