Okay, so I did a quick test setup and it seems to be working.
I used 1 SX6036 and 2 Cisco C3750E switches, all having VLAN 222 tagged and connected in between as follows:
C3750E-A, Te1/0/1 => C3750E-B, Te1/0/1
SX6036, Eth1/1 => C3750E-A, Te1/0/2
SX6036, Eth1/2 => C3750E-B, Te1/0/2
Here is the...