Your computer isn't likely configured to route DHCP requests and/or perform NAT (network address translation). On top of that your ISP may not allow you to lease more than one public IP even if the empeg's DHCP request is getting through.
Set the empeg to a specific (not DHCP) non-routed IP address (something like 192.168.1.2) and also set the secondary NIC (the one connected to the empeg) to not use DHCP and assign it an address in the same subnet (like 192.168.1.1), make the subnet mask on both 255.255.255.0 where applicable.
This in effect creates a private network off the internet inside your house just for your empeg. I'm guessing it should work.