Cisco WLC Broadcast Forwarding same SSID, but different VLANs

[m.stoedtner]

Hello Cisco Community,

currently we have the following situation:

we are running an enterprise Wireless network with a SSID which is mapped into a "vlan_dummy" and vlan ID 4094. The Cisco ISE authenticates the Client and returns the corresponding VLAN ID in which the client has to fall.

let´s say:

client A connects to the SSID and ISE answers with VLAN ID 100

client B connects to the SSID and ISE answers with VLAN ID 200

The client is authenticated and falls to the corresponding VLAN.

Great this is how it should work, but now we got the following request:

in VLAN 100 there are already clients connected, now when a Client in VLAN 200 connects via the same SSID, does the clients in VLAN 100 recieves Broadcast messages from the clients in VLAN 200 during connection and afterwards?

we have broadcast forwarding globally enabled?

could this be the reason for this behaviour?

[Ric Beeching]

Hi,

Based on your setup the clients already in VLAN 100 should not receive broadcasts from clients in VLAN 200 unless there is some sort of relay that sends them between VLANs, e.g. multicast routing.

Broadcasts are generally Layer 2 and therefore isolated to their VLAN only. The WLC merely supports forwarding all broadcast frames both to and from the wireless/wired networks that it has an interface in. 

This is disabled by default because each broadcast frame must be unicast to the end wireless clients and that can consume valuable airtime.

Ric