IGMP snooping problem

Hi,

I'm testing IGMP snooping on a router which has 4 LAN ports.

# brctl show
bridge name     bridge id                      STP enabled     interfaces
br0                  8000.00037fbef050       yes                   eth0

          eth1

          eth2

          eth3

          ath0

          ath1

          ath2

          ath3

ath0, 1, 2, 3 are WIFI.
IGMP snooping works well with this configuration.

The router supports a "switch mode", namely the 4 LAN ports connected
to a on-board switch.
In this mode, there is only a eth0, no eth1,2,3.
One benefit of this mode is that the traffic between LAN ports don't
need to go to CPU.
The LAN ports traffic will be handled by hardware switch directly.

# brctl show
bridge name     bridge id                      STP enabled     interfaces
br0                  8000.00037fbef050       yes                   eth0

          ath0

          ath1

          ath2

          ath3

In this mode, the IGMP snooping among the 4 LAN ports won't work.

Any idea how to resolve this problem?

Thanks,
Lin Ming