Causes of Errdisable
This feature was first implemented in order to handle special collision situations in which the switch detected excessive or late collisions on a port. Excessive collisions occur when a frame is dropped because the switch encounters 16 collisions in a row. Late collisions occur after every device on the wire should have recognized that the wire was in use. Possible causes of these types of errors include:
* A cable that is out of specification (either too long, the wrong type, or defective)
* A bad network interface card (NIC) card (with physical problems or driver problems)
* A port duplex misconfiguration
A port duplex misconfiguration is a common cause of the errors because of failures to negotiate the speed and duplex properly between two directly connected devices (for example, a NIC that connects to a switch). Only half-duplex connections should ever have collisions in a LAN. Because of the carrier sense multiple access (CSMA) nature of Ethernet, collisions are normal for half duplex, as long as the collisions do not exceed a small percentage of traffic.

Explanation
Locator ID Separation Protocol (LISP) is a network architecture and protocol that implements the use of two namespaces instead of a single IP address:
+ Endpoint identifiers (EIDs)-assigned to end hosts.
+ Routing locators (RLOCs)-assigned to devices (primarily routers) that make up the global routing system.
Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_lisp/configuration/xe-
3s/irl-xe-3s-book/irl-overview.html

+ From the output of WLC -show interface summary ||, we learned that the WLC has four VLANs: 999, 14, 15 and 16. + From the -show ap config general FlexAP1 || output, we learned that FlexConnect AP has four VLANs: 10, 11, 12 and 13. Also the WLAN of FlexConnect AP is mapped to VLAN 10 (from the line -WLAN 1: ...... 10 (AP-Specific)).
From the reference at: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-1/Enterprise-Mobility-8-1-Design-Guide/Enterprise_Mobility_8-1_Deployment_Guide/ch7_HREA.html
FlexConnect VLAN Central Switching Summary Traffic flow on WLANs configured for Local Switching when FlexConnect APs are in connected mode are asfollows:
+ If the VLAN is returned as one of the AAA attributes and that VLAN is not present in the FlexConnect APdatabase, traffic will switch centrally and the client is assigned this VLAN/Interface returned from the AAAserver provided that the VLAN exists on the WLC. (-> as VLAN 15 exists on the WLC so the client inconnected mode would be assigned this VLAN -> Answer 'When the AP is in connected mode, the client will beplaced in VLAN 15' is correct) + If the VLAN is returned as one of the AAA attributes and that VLAN is not present in the FlexConnect APdatabase, traffic will switch centrally. If that VLAN is also not present on the WLC, the client will be assigned aVLAN/Interface mapped to a WLAN on the WLC. + If the VLAN is returned as one of the AAA attributes and that VLAN is present in the FlexConnect APdatabase, traffic will switch locally. + If the VLAN is not returned from the AAA server, the client is assigned a WLAN mapped VLAN on thatFlexConnect AP and traffic is switched locally.
Traffic flow on WLANs configured for Local Switching when FlexConnect APs are in standalone mode are asfollows:
+ If the VLAN returned by the AAA server is not present in the FlexConnect AP database, the client will be puton a default VLAN (that is, a WLAN mapped VLAN on a FlexConnect AP) (-> Therefore answer 'While the APis in standalone mode, the client will be placed in VLAN 10' is correct). When the AP connects back, this clientis de-authenticated (-> Therefore answer 'When the AP transitions to connected mode, the client will be de-authenticated' is correct) and will switch traffic centrally.