Network measurements are essential for assessing performance issues, identifying and locating problems. Two common strategies are: the passive approach that attaches specific devices to links in order to monitor the traffic that passes by the network and the active approach that generates explicit control packets in the network for measurements. One of the key point is to minimize the overhead in terms of hardware, software and maintenance cost and of additional traffic. In this paper, we study the problem of assigning tap devices for passive monitoring and beacons for active monitoring. Minimizing the number of devices and finding optimal strategic locations is a key issue, mandatory for deploying scalable monitoring platforms. We propose new solutions based on an Integer Linear Programming formulation.