Controller Based WLANs

Product and Software: This article applies to all Aruba controllers that run ArubaOS 3.4 and later.

IGMP Snooping and IGMP Proxy

These two features can achieve the same goal: reduce traffic replication and save air time. The controller maintains a mapping table and forwards multicast traffic only to the hosts that have joined the specific multicast group.

• IGMP snooping: The controller listens to IGMP messages coming off the wireless client on a per VLAN basis (IGMP snooping option under the VLAN interface). The controller uses this information to build a multicast forwarding table that defines mapping of a particular multicast group, tunnels, and outgoing port(s) or interface(s) that have active members subscribed to the multicast traffic stream. However, IGMP snooping lacks the support for user roaming when IP mobility is on. If a user roams to a new VLAN with an old IP address, the upper layer does not to send out a new IGMP join and services are disrupted.
  
  
• IGMP proxy: The controller joins multicast group(s) on behalf of mobile clients. This action reduces the number of IGMP messages and also addresses the mobility issues, because the controller is aware of the client roaming and the new VLAN.

In both cases, user VLANs must be trunked to the uplink router. This connection ensures that the router can receive and process the IGMP messages.

Only IGMP v1 and v2 are supported.