DellPowerConnect W- Series ArubaOS 6.2 | User Guide IPMobility | 492
Chapte r 28

IP Mobility

A
mobility domain
is a group of Dell controllersamong which a wireless user can roam without losing their IP
address.Mobility domains are not tied with t he master controller,thus it is possible for a user to roam between Dell
controllersmanaged by different master Dellcontrollers as long as allo fthe Dell controllers belong to the same
mobility domain.
You enableand configure mobility do mains only on Dell controllers. No additional software or configuration is
requiredon wireless clients to allow roaming within the domain.
Topics in this chapter include:
l"UnderstandingDell Mobility A rchitecture"on page 4 92
l"ConfiguringMobility D omains" on page 493
l"TrackingMobile Users" on page 497
l"ConfiguringAdvanced Mobility Functions" on page 4 99
l"UnderstandingBridge Mode Mobility Deployments" on page 50 3
l"EnablingMobility Multicast" on page 504

Understanding De ll Mobility Architecture

Dell’slayer-3 mobilit y solution is based on the Mobile IP protocol standard, as described in RFC 3344 , “IP Mobility
Supportfor I Pv4”. This standard addresses users who need both network connectivity and mobility within the work
environment.
Unlikeo therlayer-3 mobility solutions, a D ellmobility solution does not require that you install mobility software
or performadditio nalconfiguration on wireless clients. The Dell controllers performall functions that enable clients
to roam within the mobility domain.
In a mobility domain, a
mobileclient
is a wireless client that can change its point of attachment from one network
to another within the domain. A mobile client receives an I P address (
a homeaddress
) on a
homenetwork
.
A mobile client can detach at any time from its home network and reconnectt o a
foreignnetwork
(any network
other thant hemobi leclient’s home network) within the mobility domain. When a mobile client is connected to a
foreignnetwork, it is bound to a
care-ofaddress
that reflects its current point of attachment. A care-of address is the
IP address of the Dell controller in the foreignnetwork with which the mobile client is assoc iated.
The
homeagent
for the clienti s the controllerwhere the client appears for the first time when it joins the mobility
domain. Thehome agent is the si nglepoint of contact for the client when the clientroams. The
foreignagent
for the
client is the controllerwhich handles all Mobile IP communication with the home agent on behalf of the client.
Traffic sent to a client’s home addressis intercepted by the home agent andtunneled for delivery to the client on
the foreignnetwork. On the foreign network, the foreignagent delivers the tunneled data to the mobile client.
Figure1 50 shows the routing of traffic from Host A to Mobile Client B when the client is away from its home
network.The client’s care-of address is the IP address of the Dell controller in the foreign network.
The numbersin the Figure 150 co rrespondto t he followingdescriptions:
1. T rafficto Mobile Client B arrives at the client’s home network via standard IP routing mechanisms.