After WX3540H AP registered and went online, it was dropped soon

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A site uses WX3540H as the AC, and the AP uses WA5320. After the on-site configuration is completed, it can go online successfully, but soon it is found that the AP is offline and the log on the AC indicates that the neighbor has timed out. 

For details, refer to the following tips: 

%Oct 29 10:34:36:438 2020 FHSU-AC3540-01 CWS/4/CWS_AP_DOWN: CAPWAP tunnel to AP WA5320-01 went down. Reason: Neighbor dead timer expired. 

%Oct 29 10:34:36:441 2020 FHSU-AC3540-01 APMGR/6/APMGR_AP_OFFLINE: AP FHSU-JR-WA5320-01 went offline. State changed to Idle.  

Since the site can go online normally, it should have nothing to do with the registered configuration. Check the AC configuration and find that the site has been forwarded locally. It is suspected that there is a problem with the issued MAP file. 

Let the customer feedback the configuration of the MAP file. 

 MAP file:  

system-view 

vlan 2801 

quit 

vlan 21 

description OA 

quit

 interface GigabitEthernet 1/0/1 

port link-type trunk 

port trunk permit vlan 21 2801 

undo port trunk permit vlan 1

It is found that undo port trunk permit vlan 1 in the map configuration. If the interface does not allow vlan 1 to pass, it will cause the int vlan 1 virtual interface on the AP to go down and cause the AP to go offline. 

After this configuration is deleted, the problem is solved .