Two subnets on a single NIC?


I’m trying to start a DHCP server on my webmin box in order to set up TFTP server. I installed a DHCP server webmin module and configured it, however the service won’t start. Here’s what I can see in the logs:

No subnet declaration for eth0 (my external IP here).
dhcpd: ** Ignoring requests on eth0. If this is not what
dhcpd: you want, please write a subnet declaration
dhcpd: in your dhcpd.conf file for the network segment
dhcpd: to which interface eth0 is attached. **
dhcpd: Not configured to listen on any interfaces!

I did set an interface to listen on in dhcp config (eth0), however eth0 is the only interface available on this box and it’s associated with the external static IP. I did try to create a virtual interface (eth0:1) but unfortunately my dhcp config doesn’t seem to see it. When I try to set a gateway to this virtual interface it becomes default gateway of the server and it disappears from network and only becomes available when I delete the gateway entry for the virtual interface. So what should I do? I feel the solution should be very straightforward and I’m overlooking something here. Please advise.