Dell PowerConnect W-Airwave Configuration Manual page 160

The home agent for the client is the controller where the client appears for the first time when it joins the
mobility domain. The home agent is the single point of contact for the client when the client roams. The
foreign agent for the client is the controller which handles all Mobile IP communication with the home
agent on behalf of the client. Traffic sent to a client's home address is intercepted by the home agent and
tunneled for delivery to the client on the foreign network. On the foreign network, the foreign agent delivers
the tunneled data to the mobile client.
A mobility domain is a group of Aruba controllers among which a wireless user can roam without losing
their IP address. Mobility domains are not tied with the master controller, thus it is possible for a user to
roam between controllers managed by different master controllers as long as all of the controllers belong to
the same mobility domain.
You enable and configure mobility domains only on Aruba controllers. No additional software or
configuration is required on wireless clients to allow roaming within the domain.
Before configuring a mobility domain, you should determine the user VLAN(s) for which mobility is
required. For example, you may want to allow employees to be able to roam from one subnetwork to
another. All controllers that support the VLANs into which employee users can be placed should be part of
the same mobility domain.
A controller can be part of multiple mobility domains, although Aruba recommends that a controller belong
to only one domain. The controllers in a mobility domain do not need to be managed by the same master
controller.
You configure a mobility domain on a master controller; the mobility domain information is pushed to all
local controllers that are managed by the same master controller. On each controller, you must specify the
active domain (the domain to which the controller belongs). If you do not specify the active domain, the
controller will be assigned to a predefined "default" domain.
Although you configure a mobility domain on a master controller, the master controller does not need to be
a member of the mobility domain. For example, you could set up a mobility domain that contains only local
controllers; you still need to configure the mobility domain on the master controller that manages the local
controllers. You can also configure a mobility domain that contains multiple master controllers; you need to
configure the mobility domain on each master controller.
Table 73 Controllers in a Mobility Domain
On a master controller:
Configure the mobility domain, including the entries
in the home agent table (HAT).
You can enable or disable IP mobility in a virtual AP profile (IP mobility is enabled by default). When IP
mobility is enabled in a virtual AP profile, the ESSID that is configured for the virtual AP supports layer-3
mobility. If you disable IP mobility for a virtual AP, any clients that associate to the virtual AP will not have
mobility service.
160 | Aruba Configuration Reference
On all controllers in the mobility domain:
Enable mobility (disabled by default).
Join a specified mobility domain (not required for
"default" mobility domain).
AirWave Wireless Management Suite | Configuration Guide