Users Guide

Dell PowerConnect ArubaOS 5.0 | User Guide IP Mobility | 399
Chapter 19
IP Mobility
A mobility domain is a group of Dell 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 Dell controllers. No additional software or configuration is
required on wireless clients to allow roaming within the domain.
This chapter describes the following topics:
z “Dell Mobility Architecture” on page 399
z “Configuring Mobility Domains” on page 400
z “Tracking Mobile Users” on page 404
z “Advanced Mobility Functions” on page 406
z “Mobility Multicast” on page 409
Dell Mobility Architecture
Dell’s layer-3 mobility solution is based on the Mobile IP protocol standard, as described in RFC 3344, “IP
Mobility Support for IPv4”. This standard addresses users who need both network connectivity and mobility
within the work environment.
Unlike other layer-3 mobility solutions, an Dell mobility solution does not require that you install mobility
software or perform additional configuration on wireless clients. The Dell controllers perform all functions that
enable clients to roam within the mobility domain.
In a mobility domain, a mobile client is a wireless client that can change its point of attachment from one network
to another within the domain. A mobile client receives an IP address (a home address) on a home network.
A mobile client can detach at any time from its home network and reconnect to a foreign network (any network
other than the mobile client’s home network) within the mobility domain. When a mobile client is connected to
a foreign network, it is bound to a care-of address that reflects its current point of attachment. A care-of address is
the IP address of the Dell controller in the foreign network with which the mobile client is associated.
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.
Figure 70 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 numbers
in the Figure 70 correspond to the following descriptions:
1. Traffic to Mobile Client B arrives at the client’s home network via standard IP routing mechanisms.
2. The traffic is intercepted by the home agent in the client’s home network and tunneled to the care-of address
in the foreign network.
3. The foreign agent delivers traffic to the mobile client.