Firewall/NAT

I have used PFsense alot in the past (as home firewall) and recently at work we would like to allow our developers (who use VMs) located outside the european union the ability to have administrative rights on their machines. Due to several laws, the inability of some software to use NAT we had hoped to get a transparent firewall working.

Currently we have tried several SW firewalls without sucess, and somehow it feels as if vmware is the issue..?

Monowall is setup with 3 Nics, 1 with physical connection to our corporate network, and 2 "dummy" networks.

I have followed the transparent bridge guide in my setup, and i have a VM-client on the bridged OPT1 (which is a internal dummy network on the ESX host) along with the monowall-VM on the same internal network.

the client can ping the "outside" interface of monowall, but it is not able to reach the default gateway (which is not set to monowall, but the "real" gw).

Firewall rules are set to allow any on all interfaces, just for testing.

Have we set this up way off, or its vmware thats messing with us ?

Have to make a first reply as we found the issue this morning, right after i posted this 

in order for traffic to be passed, promisicous mode needs to be enabled on the vSwitch. The question is now, will it have negative impact on the performance ? (since the default vswitch handles traffic for many Vms).