are controllers defined as anchors for WLANs. Clients (that is, any 802.11
mobile station, such as a laptop) are always attached to one of the anchors.
You can use
mobility anchors to restrict a WLAN to a single subnet, regardless of the
client’s network entry point. Users can access a public or guest WLAN
throughout the enterprise but will still be restricted to a specific subnet.
You can also use guest WLANs to provide geographical load balancing, as WLANs
can represent a particular section of a building (such as a lobby, restaurant,
and so on).
When a client first
associates to a controller of a mobility group that has been preconfigured as a
mobility anchor for a WLAN, the client associates to the controller locally,
and a local session is created for the client. Clients can be anchored only to
preconfigured anchor controllers of the WLAN. For a given WLAN, you should
configure the same set of anchor controllers on all controllers in the mobility
When a client first
associates to a controller of a mobility group that has not been configured as
a mobility anchor for a WLAN, the client associates to the controller locally,
a local session is created for the client, and the controller is announced to
the other controllers in the same mobility group. If the announcement is not
answered, the controller contacts one of the anchor controllers configured for
the WLAN and creates a foreign session for the client on the local switch.
Packets from the client are encapsulated and delivered to the wired network.
Packets to the client are received by the anchor controller and forwarded to
the foreign controller through a mobility tunnel using EtherIP. The foreign
controller encapsulates the packets and forwards them to the client.
A 2000 series
controller cannot be designated as an anchor for a WLAN. However, a WLAN
created on a 2000 series controllers can have a 4100 series controller or a
4400 series controller as its anchor.
The L2TP Layer 3
security policies are unavailable for WLANs configured with a mobility anchor.