Software Defined Networking (SDN) and NetworkFunction Virtualization (NFV) are complementary and corecomponents of modernized networks. In this paper, we considerthe problem of reconfiguring Service Function Chains (SFC)with the goal of bringing the network from a sub-optimal toan optimal operational state. We propose optimization modelsbased on themake-before-breakmechanism, in which a new pathis set up before the old one is torn down. Our method takes intoconsideration the chaining requirements of the flows and scaleswell with the number of nodes in the network. We show that,with our approach, the network operational cost defined in termsof both bandwidth and installed network function costs can bereduced and a higher acceptance rate can be achieved, while notinterrupting the flows.