Couple of thoughts I had while reading this thread...
0) Just to be clear.. Having multiple DHCP servers on a network is just asking for trouble.. Don't do it!
If you are talking about gazzzzzman saying "(I do NOT mean turn off your ISP side DHCP if you need it )" - he wasn't advocating leaving a DHCP server on on the external network in a single nic environment (that would cause problems without vlans!) he was talking about leaving the modem's DHCP client turned on to get his public IP address from his ISP (the real external network!) and that is of course essential if you haven't got a static IP service...
