James,

What vendor wireless are you using? In 2008, we moved from fat APs with /20 
data vlans to Aruba wireless using hashed Vlan pools with /23 Vlans. The user 
only sees broadcast for their own Vlan.  We stayed with using a single primary 
SSID. (We now have an additional SSID for non-802.1X/onboarding and another for 
Guest.)

For multicast IPTV, we are using Aruba's Dynamic Multicast Optimization that 
basically converts multicast to unicast only for the clients that are 
subscribed to a particular stream.

Bruce Osborne
Network Engineer - Wireless Team
IT Network Services

(434) 592-4229

LIBERTY UNIVERSITY
Training Champions for Christ since 1971

-----Original Message-----
From: James Andrewartha [mailto:[email protected]] 
Sent: Thursday, February 20, 2014 3:37 AM
Subject: Broadcast/multicast from multiple VLANs on a single SSID

Hi list,

We moved to a single WPA2-Enterprise SSID with RADIUS responses dropping users 
into a particular VLAN at the start of the year. However, multicast and 
broadcast traffic is seen by all clients, regardless of VLAN. After some 
thought, this makes sense because the SSID has a common group temporal key for 
broadcast/multicast. However I was wondering if all clients had to have the 
same GTK, or if it's possible (or if some vendor even implements) having a 
different one for clients on different VLANs.

We are probably going to split up the clients across multiple SSIDs again, as 
we're seeing Bonjour instability (you try telling a teacher to plug into a 
cable after using AirPlay last year), which may be caused by too much 
broadcast/multicast traffic or possibly just Bonjour not handlins seeing 
queries from devices on different VLANs.

--
James Andrewartha
Network & Projects Engineer
Christ Church Grammar School
Claremont, Western Australia
Ph. (08) 9442 1757
Mob. 0424 160 877

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