What should I do if the capwap tunnel failed?

Here are the possible reason:

a) Communication between the AP and the AC is abnormal.

1) The AP fails to get the IP address.

2) The AP fails to get the Option 138 field.

3) The AP fails to ping the AC to create the tunnel.

4) The CAPWAP UDP ports 5246 and 5247 are discarded or filtered out by an intermediate device.

b) The AC and AP are in abnormal status.

1) The AP cannot go online due to a high AC CPU usage.

You can type 'show cpu' to check the CPU usage of AC device

2) The AC license is insufficient.

You can type 'show ac-config', 'show license' and 'show ap-config summary' to check the license status.

3) The AC and AP version span is large (recommend to use same version for AP and AC).

4) The AP name is not unique. Here is the related log:

19 16:37:19: CD-AC4 %APMG-6-AP_ADD: Add AP(1414.4b5d.03af) fail. Online-AP(1414.4b5d.097f) with same name(XS10A4-1) has exist in this AC  

You can modifies the name of online AP to deal with it.

Troubleshoot:

In the end, you can collect the following information and contact TAC team to solve this issue.

a) Collect the following information on the AC:

show version

show running

show ac-config

show license

show ap-config summary

show capwap sta

show cpu

show memory

show ip route

show ip interface brief

b) Collect the following information on the AP:

show version

show ap-mode

show capwap sta

show ip route

show log

show capwap client state