About tunneling client traffic, from the controller online help:
Client data tunnel
(Only available when Access control is enabled.)
When a VSC is access-controlled, client traffic that is sent between the AP and controller can be carried in the client data tunnel. This provides the following benefits:
- User traffic is segregated from the backbone network and can only travel to the controller.
- Underlying network topology is abstracted enabling full support for L2-connected users across routed networks.
The client data tunnel is always used when the connection between a controlled AP and its controller traverses at least one router. The client data tunnel supports NAT traversal, so it can cross routers that implement NAT.
Optionally, the client data tunnel can also be used when a controlled AP and its controller are on the same subnet. To do this, enable the Always tunnel client traffic option.
Performance and security settings for the client data tunnel can be customized by selecting Controller >> Controlled APs > Client data tunnel.
Always tunnel client traffic
Use this option to manually force wireless client traffic into the client data tunnel, even when an AP is on the same layer 2 subnet as the controller.