Aruba – AP Troubleshooting

In order to make the WLAN function, the access points need connectivity to the controller.  Let’s review what an AP does during the boot process

Acquire IP address (can be static or acquired from DHCP)

  • IP address is required for communication with the controller using PAPI and GRE
  • To verify the access point properly acquires an IP you will need console access to the AP

Discover Controller

  • The AP goes through the following process in trying to discover a controller
  1. Statically assigned
  2.  DHCP Vendor Option 43
  3. ADP Multicast: Group Address 239.0.82.11 (requires multicast routing to be enabled on infrastructure)
  4. ADP L2 Broadcast
  5. DNS (aruba-master.<localsuffix>
  • The AP will follow the sequence exactly as above.  Once the AP learns a controller address, it terminates the discovery process and attempts to communicate with the learned address.  If the AP doesn’t receive a response from the learned address, then the AP will initiate a full reboot and start the process again

Update Code if necessary

  • AP Compares the code level to the controller’s code level
  • If the code revision matches the AP will continue the boot process
  • If the code revision does not match the AP will obtain the new code from the controller using FTP (TFTP is used on the initial join or if the AP is purged
  • The AP will automatically reboot after the code upgrade/downgrade
  • “show ap database” shows the current status of each AP (will list if upgrading, rebooting, etc)

Obtain Configuration Information

  • Once an AP connects to a controller and has compatible code, it will receive its configuration over PAPI
  • “show ap config ap-name <ap-name>” will show the AP configuration being pushed to the AP

Build GRE Tunnel

  • GRE is used to carry all of the wireless traffic between the AP and the local controller
  • A GRE tunnel is created per SSID per AP
  • The AP System Profile Controller LMS-IP setting tells the AP which controller the AP should terminate with
  • Be sure to allow Protocol 47 between the controllers and APs
  • “show ap debug system-status ap-name <ap-name>” – shows the communication status between the controller and AP
  • “show datapath tunnel table”shows the GRE tunnels established with the controller (look for prt 47)
  • “show ap debug counters”shows how many times an AP has rebooted or bootstrapped

Enable Radio

  • Once the GRE tunnel has been established the Radios will become enabled
  • “show profile-errors” – shows the list of invalid user created profiles.  An invalid user profile could cause the AP not to broadcast its assigned SSIDs.

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