SureBackup: how to support multple gateways within a VLAN?

[mikeely]

One of the networks I'm trying to map looks a bit like one of those old houses that's been added to half a dozen times, where you go up into the attic and there's a whole roof inside the outer roof, when the hot water goes out it only goes out for half the house, and so on.

The network has six segments, each with its own gateway, and it's the one that the majority of our VMs use. Trying to add multiple vNICS to the same interface fails with "vNIC with such isolated network connected already exists."

Trying to figure out which of the hundred-plus VMs that use the VLAN in question are on which network segment is simply not feasible. How do I thread this needle?