EtherCAT cannot use a standard Ethernet Switch.  If you want a Switch because it makes the topography of the wiring more convenient, then you need an an EtherCAT Swtich/hub such as the Beckhoff CU1128.

Using a switch makes no difference to the logical layout of the network.  The branches are NOT isolated so if any device fails or there is a disconnection, then all the devices on the network will go into error.