PPTP with dhcp only for clients

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http://unix.stackexchange.com – I have a local network at home with a router and a small server. The router manages the local network (DHCP, etc) but does not support PPTP. On the server (Ubuntu 12.04) I set up pptpd and this is working fine ... except that the dhcp3 server started by pptpd is now conflicting with the router. My other systems get answers from two DHCP servers - and not all of them are able to handle it properly (namely my Android tablet). I have no idea where to start fixing this (except using static IP addresses for my VPN). Any ideas would be appreciated. ()