Both devices have 3 interfaces each. As long as they are configured on the same subnet — random interface, random IP on each device, traffic passes between them. Here're the parsed vmx and networking files. I don't have a VMnet0 on the host. There must be something I'm missing or something that the hypervisor is doing automatically.
$ grep "ethernet" ASAv.vmwarevm/ASAv941.vmx
ethernet0.present = "TRUE"
ethernet0.addressType = "generated"
ethernet0.connectionType = "custom"
ethernet0.virtualDev = "e1000"
ethernet0.startConnected = "FALSE"
ethernet1.present = "TRUE"
ethernet1.addressType = "generated"
ethernet1.connectionType = "custom"
ethernet1.virtualDev = "e1000"
ethernet1.startConnected = "FALSE"
ethernet2.present = "TRUE"
ethernet2.addressType = "generated"
ethernet2.connectionType = "custom"
ethernet2.virtualDev = "e1000"
ethernet2.startConnected = "FALSE"
ethernet0.pciSlotNumber = "32"
ethernet1.pciSlotNumber = "33"
ethernet2.pciSlotNumber = "34"
ethernet0.generatedAddressOffset = "0"
ethernet1.generatedAddressOffset = "10"
ethernet2.generatedAddressOffset = "20"
ethernet0.vnet = "VMnet0"
ethernet3.present = "TRUE"
ethernet3.virtualDev = "e1000"
ethernet3.startConnected = "FALSE"
ethernet3.wakeOnPcktRcv = "FALSE"
ethernet3.addressType = "generated"
ethernet3.pciSlotNumber = "36"
ethernet3.generatedAddressOffset = "30"
ethernet4.present = "FALSE"
ethernet5.present = "FALSE"
ethernet6.present = "FALSE"
ethernet7.present = "FALSE"
$
$ grep "ethernet" ASAv\ 2.vmwarevm/ASAv941.vmx
ethernet0.present = "TRUE"
ethernet0.addressType = "generated"
ethernet0.connectionType = "custom"
ethernet0.virtualDev = "e1000"
ethernet0.startConnected = "FALSE"
ethernet1.present = "TRUE"
ethernet1.addressType = "generated"
ethernet1.connectionType = "custom"
ethernet1.virtualDev = "e1000"
ethernet1.startConnected = "FALSE"
ethernet2.present = "TRUE"
ethernet2.addressType = "generated"
ethernet2.connectionType = "custom"
ethernet2.virtualDev = "e1000"
ethernet2.startConnected = "FALSE"
ethernet0.pciSlotNumber = "32"
ethernet1.pciSlotNumber = "33"
ethernet2.pciSlotNumber = "34"
ethernet0.generatedAddressOffset = "0"
ethernet1.generatedAddressOffset = "10"
ethernet2.generatedAddressOffset = "20"
ethernet0.vnet = "VMnet0"
ethernet3.present = "TRUE"
ethernet3.virtualDev = "e1000"
ethernet3.startConnected = "FALSE"
ethernet3.wakeOnPcktRcv = "FALSE"
ethernet3.addressType = "generated"
ethernet3.pciSlotNumber = "36"
ethernet3.generatedAddressOffset = "30"
ethernet4.present = "FALSE"
ethernet5.present = "FALSE"
ethernet6.present = "FALSE"
ethernet7.present = "FALSE"
$
$ sed -En "s/.*(VNET_[0-9]*).*/\1/p" /Library/Preferences/VMware\ Fusion/networking | uniq | sort
VNET_1
VNET_10
VNET_8
VNET_9
VNET_91
VNET_92
VNET_93