When enabled, passive beaconing allows a stranded mesh access point to broadcast its debug messages over-the-air using a 802.11b/g radio. A neighboring mesh access point that is listening to the stranded mesh access point and has a connection to a controller, can pass those messages to the controller over CAPWAP. Passive beaconing prevents a mesh access point that has no wired connection from being stranded.
Debug logs can also be sent as distress beacons on a nonbackhaul radio so that a neighboring mesh access point can be dedicated to listen for the beacons.
The following steps are automatically initiated at the controller when a mesh access point loses its connection to the controller:
- Identifies the MAC address of a stranded mesh access point
- Finds a nearby neighbor that is CAPWAP connected
- Sends commands through remote debug
- Cycles channels to follow the mesh access point
You only have to know the MAC address of the stranded AP to make use of this feature.
A mesh access point is considered stranded if it goes through a lonely timer reboot. When the lonely timer reboot is triggered, the mesh access point, which is now stranded, enables passive beaconing, the anti-stranding feature.
This feature can be divided into three parts:
- Strand detection by stranded mesh access point
- Beacons sent out by stranded mesh access point
- Latch the 802.11b radio to a channel (1,6,11)
- Enable debugs
- Broadcast the standard debug messages as distress beacons
- Send Latest Crash info file
- Receive beacons (neighboring mesh access point with remote debugging enabled)
Deployed mesh access points constantly look for stranded mesh access points. Periodically, mesh access points send a list of stranded mesh access points and SNR information to the controller. The controller maintains a list of the stranded mesh access points within its network.
When the debug mesh astools troubleshoot mac-addr start command is entered, the controller runs through the list to find the MAC address of the stranded mesh access point.
A message is sent to the best neighbor to start listening to the stranded access point. The listening mesh access point gets the distress beacons from the stranded mesh access point and sends it to the controller.
Once a mesh access point takes the role of a listener, it does not purge the stranded mesh access point from its internal list until it stops listening to the stranded mesh access point. While a stranded mesh access point is being debugged, if a neighbor of that mesh access point reports a better SNR to the controller than the current listener by some percentage, then the listener of the stranded mesh access point is changed to the new listener (with better SNR) immediately.
End-user commands are as follows:
- config mesh astools [enable | disable]—Enables or disables the astools on the mesh access points. If disabled, APs no longer sends a stranded AP list to the controller.
- show mesh astools stats—Shows the list of stranded APs and their listeners if they have any.
- debug mesh astools troubleshoot mac-addr start—Sends a message to the best neighbor of the mac-addr to start listening.
- debug mesh astools troubleshoot mac-addr stop—Sends a message to the best neighbor of the mac-addr to stop listening.
- clear mesh stranded [all | mac of b/g radio]—Clears stranded AP entries.
The controller console is swamped with debug messages from stranded APs for 30 minutes.