Opportunistic network defragmentation and optimization

Systems and methods include determining a defragmentation plan that changes a configuration of a network to move the network from a current state of operation to a new state of operation; updating any of the defragmentation plan and the new state of operation in response to an opportunity presented during operation of the network; and implementing one or more steps in the defragmentation plan based on the opportunity. The opportunity can be anticipated to occur at a future time and implementation of the one or more steps is conditioned on occurrence of the opportunity. For example, the opportunity can include any of a maintenance window, a network equipment change, a capacity change in the network, a change to demand in the network, an external event including weather, and changes in links in the network. Also, the opportunity can include a fault.