A mobile ad hoc network is a group of mobile, wireless nodes which cooperatively and spontaneously form an IP-based network. In order to make computing and communication, a node in an IP-based network must be configured with an IP address. On the other hand, the main problem in an ad hoc network is the mobility of the nodes which can lead to frequent and unpredictable topology changes (network partitions and merge). In this environment, a centralized administration is an impossible approach so automated dynamic assignment of IP addresses is a desirable goal. One key challenges to mobile ad hoc network is the resolution of addresses when two or more partitions merge. In this paper, we propose a new approach to merge partitions in a mobile network, based on an updating of DHCP (which is a protocol designed to wired network). This solution implements a new DHCP client/server, which can detect IP conflicts. Finally, we evaluate the performance of the solution through simulation experiments.