VLANs or multiple ethernet cards?

unknown wrote:

that should give you enough with what you can do with mesa ethernet
 

That's not my concern. I remember hearing somewhere that the Mesa ethernet link takes over the whole interface, and prevents other traffic from using it too. Wherever I heard that, nothing was said about VLANs, so I assume they were using the physical interface. If the mesa link wants to take over the VLAN that's fine, but if it takes the whole physical interface in spite of VLANs being configured, that would be irritating.

Multiple Ethernet cards.
And Mesa always wired directly to the PC, not through HUB or Switch or VLAN.
Now that is out of the way, i have tested Mesa cards through cheap switches (non manageable) and it worked for me without issues for weeks at a time, but i would never run a production machine through it.
I do not know if EtherCAT works through any of those as i never tested this. But i have seen something used for EtherCAT redundancy several years back at a machine show, for some strange reason i did not pay attention.

I would put 2 NICS in the PC, daisy chain one NIC to your Ethernet slaves and use the either to connect your PC to your network, with or without a VLAN.

Ethercat is likened to a high speed train with packets getting on and off without the train stopping... so no benefit in more complex networking