New install - cannot get access to internet

Hello,

I've read a couple of posts like this, but none of them solves my issue.

I have installed UTM9.1 on a barebones miniITX pc, with four NICS. Eth0 is plugged into my WAN port on my modem, and ETH1 is plugged into my main PC. (eventually it will go to a switch).

The "interfaces" has Internal and External. I can correctly set up the EXTERNAL interface so that it picks up an external WAN Ip address from my ISP.

However, i CANNOT get my network pcs to access the internet at all.

Things i have verified:

1. DHCP is up and running
2. DNS is set to "my ISP dns"
3. i disabled the default firewall rules and added a new one that opens everything up at the top. 'Any' to 'Any' on 'Any' service, at ALL TIMES. Action to ACCEPT.
4. All network services like IPS etc have been turned OFF.

There is the default NAT rule in the NAT area... INTERNAL --> EXTERNAL.

Things I haven't done:

1.I Haven;t done anything with MAQUERADING though... not sure what that is, or whether it is necessary here.
2. I haven't set up a bridge of any kind (in the interfaces page). I don;t think i need a bridge though... as i have plenty of EthX sockets?

If i open the firewall LIVE LOG, all the entries in there are RED --> default DROP ... but i can't find anywhere in the UTM9 settings where i can change the default action to ACCEPT.

Please can anyone fathom a guess as to what i am missing and why my PCs can't access the net.

It can;t be the IPS / AV as these are all turned off. It could be the interfaces setup... maybe this "bridging" thing. But i thought i didn't need to worry about bridges.

Any advice gratefully received.

Cheers all.