Dell 6.2 Enabling Mobility M ulticast

Enabling Mobility M ulticast

Internet Protocol (IP) multicast is a network addressing method usedt o simultaneouslydeliver a single stream of

information from one sendert o multiple clients on a network. Unlike broadcast traffic, which is meant for all hosts

in a singledomain, multicast traffic is sent only to those specific hosts who are configuredto receive such traffic.

Clients who wantt o receivemulticast traffic can join a multicast group via IGMP messages.Upst reamrouters use

IGMP message information to compute multicast routing tables and determine the outgoing interfaces for each

multicast groupst ream.

In ArubaOS3.3.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

wouldnot be availableat its new destination, and multicast traffic from the client couldbe interrupted. ArubaOS 3.4

and latersupports mobility multicast enhancements that provide uninterruptedstreaming of multicast traffic,

regardlessof a client's location.

The mobility controller is always aware of the client's location, so t he controllercan joi n multicast group(s) on behalf

of that mobile client. This feature, called Proxy IGMP, allows the controller to join a multicast group and suppresses

the client’s IGMP control messages to the upstream multicast router. (The client's IGMP control messages wi ll,

however,st illbe used by controllert o maintaina multicast forwarding table.) The multicastI GMPt rafficoriginating

fromt hec lientw illi nsteadbe s ent fromthe controller’s incoming VLAN interface IP.

The IGMP proxy feature includesbot h a host implementation and a router implementation. An upstream router sees

a controllerrunning IGMP proxy as a host ; a client attached to the controller would see the controller as router.

WhenProxy IGMP i s enabled,all multicast clients associated with the controller are hidden from theupstream

multicast device or router.

NOTE:The new er IGMPproxy feature and the older IGMP snooping feature cannot be enabled at thesame tim e, as bothfeatures

addm embership information to multicast group table. For most multicast deployments, youshould enabl e theIGMP Proxy feature on

all VLAN interfacesto manage all themulticast membership requirements on the controller. If IGMP snooping is configured on some

ofthe interfaces, there is a greater chance that multicast information transfersmay be interrupted.

IGMP proxy must be enabledor disabled on each individual interface. To use the IGMP proxy ensurethat the

VLANs on the Dell controllers are extendedt o the upstream router.E nablingIGMP proxy enables IGMP on t he

interface andsets the querierto t heco ntrolleritself. You must identify the controller port fromw hicht heco ntroller

sends proxyj oin information to the upstream router,and identify t heupstream router by upstream port so the

controllercan dynamically update the upstream multicast router information.

Whena client moves fromo ne controllerto another,multicast t rafficmigrates as follows:

DellPowerConnect W- Series ArubaOS 6.2 | UserGuide IPMobility | 504