An AP establishes two CAPWAP tunnels to the WLC in local mode. Both are used for data traffic and management, respectively. Because the data traffic is switched (bridged) from the AP to the Controller, where a routing device subsequently routes it, this behavior is referred to as “centrally switched.”
The “Local” or “Central Switching” mode has a significant distinction in that all traffic returns to the WLC (Controller) wherever it is! When the WLC is located far away on the WAN, and a wireless client on one VLAN tries to utilize a local resource on a different VLAN, there is a problem since extra traffic is created as a result of the round trip between the local network and the remote WLC. And sluggish links are particularly affected by it. The handling of VLAN switching is the issue that gives the most trouble, but there are additional changes that impact how things work when a WLC goes offline.
FlexConnect enables data traffic to be switched locally rather than returning to the Controller. In essence, it makes the AP act as an autonomous AP while yet being controlled by the WLC. In this mode, even if the AP loses contact with the Controller, it can continue to operate. Additionally, it would be best to use FlexConnect whenever you need to transfer traffic locally.
A FlexConnect AP can, on a per-WLAN basis, either tunnel client data in CAPWAP to the Controller (Central Switching) or have client data egress at the AP’s LAN port (Local Switching).
FlexConnect is generally used in branch setups without a controller on the branch site. These APs can register with a controller at your Central Location or Headquarters. As a result, traffic won’t tunnel back to the CL/HQ WLC but will instead end at your branch switch.
For roaming, you must include those FlexConnect AP in a FlexConnect Group if you want to roam between those APs in your branch. Then, to enable fast roaming, only essential information is transmitted between those APs.