Virgin Media and UTM - no internet

Hi,

I've got a customer who has Virgin Media Superfast connection using their Superhub 3 router. I've switched this to modem mode, plugged in a laptop and can access the internet absolutely fine. If I connect the SG125 UTM, eth1 and set it as ethernet connection with a dynamic IP, the link/connection shows UP, I get a dynamic IP but cant access anything on the internet, cant even ping 8.8.8.8.

I've set many UTMs so have done the basics of masq rule, dns and know this isnt a simple fix.

So to cut a long story short, it seems other people have the same issue when using Cisco routers with Virgin. The solution is to clear the broadcast flag on the NIC that connects to the Virgin Media router with this command

"ip dhcp client broadcast-flag clear"

or disable broadcast flag on the NIC

My question is, how can this be done on the UTM, if it can? I've done some googling and trawling through these forums but not found anything

Many thanks in advance