Explanation
Operation Modes
There are two modes of operation for the FlexConnect AP.
* Connected mode: The WLC is reachable. In this mode the FlexConnect AP has CAPWAP connectivity with its WLC.
* Standalone mode: The WLC is unreachable. The FlexConnect has lost or failed to establish CAPWAP connectivity with its WLC. A WAN-link outage between a branch and its central site is a example of such a mode of operation.
FlexConnect States
A FlexConnect WLAN, depending on its configuration and network connectivity, is classified as being in one of the following defined states.
* Authentication-Central/Switch-Central: This state represents a WLAN that uses a centralized authentication method such as 802.1X, VPN, or web. User traffic is sent to the WLC via CAPWAP (Central switching). This state is supported only when FlexConnect is in connected mode.
* Authentication Down/Switching Down: Central switched WLANs no longer beacon or respond to probe requests when the FlexConnect AP is in standalone mode. Existing clients are disassociated.
* Authentication-Central/Switch-Local: This state represents a WLAN that uses centralized authentication, but user traffic is switched locally. This state is supported only when the FlexConnect AP is in connected mode.
* Authentication-Down/Switch-Local: A WLAN that requires central authentication rejects new users.
Existing authenticated users continue to be switched locally until session time-out if configured. The WLAN continues to beacon and respond to probes until there are no more existing users associated to the WLAN. This state occurs as a result of the AP going into standalone mode.
* Authentication-local/switch-local: This state represents a WLAN that uses open, static WEP, shared, or WPA2 PSK security methods. User traffic is switched locally. These are the only security methods supported locally if a FlexConnect goes into standalone mode. The WLAN continues to beacon and respond to probes. Existing users remain connected and new user associations are accepted. If the AP is in connected mode, authentication information for these security types is forwarded to the WLC.

Explanation
Text Description automatically generated

Explanation
DNS: If you have configured your DHCP server to provide both option 006 (DNS server address) and option
015 (domain name) information, the AP can obtain WLC addresses from the DNS server. The process works as follows:
1. The AP gets its IP address from DHCP with options 6 and 15 configured.
2. The AP can obtain the IP address of the DNS server from the DHCP option.
3. The AP uses this information to perform a hostname lookup using
CISCO-CAPWAP-CONTROLLER.<localdomain>, which resolves to available WLC management interface IP addresses (IPv4 or IPv6, or both).
4. The AP can then perform a directed message to associate to responsive WLCs.
To prevent all APs from joining a single controller based on a DNS name resolution, the domain name may vary; this is what is done to dispatch APs to different controllers across the enterprise network, based on different domain names that are configured in their respective DNS scopes.