Technical data

Multicasting Feature

on the network. Multicasting is an advanced feature and can cause subtle changes in your

network. By default, multicasting is disabled and should be enabled only for specific

circumstances. Possible multicasting applications include:

 Broadcast via cable or satellite to IPTV (for example, Vbrick or Video Furnace)

 Any broadcast application (for example, CEO address to company)

 Distance learning (live lectures)

 Video surveillance

 Video conferencing

For multicast to work, you need to complete these four tasks:

 Enable Virtual Cell and Virtual Port on AP300/AP400s - see Configuring Virtual Cell

Support for AP300 or AP400 with the CLI and Virtual Port is Now Part of Virtual Cell

for directions.

 Enable IGMP snooping on the controller - see Configuring IGMP Snooping on

Controllers and APs

 Enable IGMP snooping on the network infrastructure including intermediary

switches. You must do this because Meru controllers do not source multicast group

membership queries. We rely (as do most controllers) on the switches to perform

that task.

 Map a Virtual Cell enabled ESS with the default VLAN - see Assigning a VLAN with

the CLI.

Configuring IGMP Snooping on Controllers and APs

Multicasting is implemented using IGMP snooping. In System Director release 3.6, IGMP

snooping was only done at the controller; the controller knew which clients were

subscribed to specific multicast streams and sent the data for the subscribed multicast

stream only to the APs with clients currently being serviced. Since the AP didn't know

which clients subscribed to the specific stream, it would send multicast streams to all

clients currently being serviced by the AP. (With Virtual Port, there would be N copies, one

for each client). This wasted airtime and created unnecessary traffic and contention.

In release 4.0 and later, IGMP snooping is done not only by the controller but also done by

AP300/AP400s (excluding AP1000) when using Virtual Cell. The controller passes the client

subscription list for multicast streams to AP300/AP400, which limits the multicast streams

to only subscribed clients, reducing wireless traffic and saving time. (There are no changes

in sending multicasts for stations connected to non-Virtual Cell ESS profiles.)

Commands to Configure IGMP Snooping

The following command is used to enable/disable IGMP snooping on the controller and APs:

igmp-snoop state [enable, disable]

Command to show igmp-snoop status:

show igmp-snoop