Users Guide

664| IP Mobility Dell Networking W-Series ArubaOS 6.5.x| User Guide
Figure 87 Bridge Mode Mobility
The roaming process occurs as follows:
1. A client begins to roam from AP1 and starts an association with AP2.
2. AP2 sends a broadcast message to all APs on the local layer-2 network, asking if any other AP has a current
session state for the roaming client.
3. Only AP1 responds to the broadcast, and sends the current session table of the client.
4. AP2 acknowledges receipt of the session table.
5. AP1 deletes the session state of the client.
6. Roaming is complete.
Enabling Mobility Multicast
Internet Protocol (IP) multicast is a network addressing method used to simultaneously deliver a single stream
of information from one sender to multiple clients on a network. Unlike broadcast traffic, which is meant for all
hosts in a single domain, multicast traffic is sent only to those specific hosts who are configured to receive such
traffic. Clients who want to receive multicast traffic can join a multicast group via IGMP messages. Upstream
routers use IGMP message information to compute multicast routing tables and determine the outgoing
interfaces for each multicast group stream.
In ArubaOS 3.3.x and earlier, when a mobile client moved away from its local network and associated with a
VLAN on a foreign controller (or a foreign VLAN on its own controller), the client’s multicast membership
information would not be available at its new destination, and multicast traffic from the client could be
interrupted. ArubaOS 3.4 and later supports mobility multicast enhancements that provide uninterrupted
streaming of multicast traffic, regardless of a client's location.
Working with Proxy IGMP and Proxy Remote Subscription
The controller is always aware of the client's location, so the controller can join multicast group(s) on behalf of
that mobile client. This feature, called Proxy IGMP, allows the controller to join a multicast group and