In this paper, we consider the problem of designing agents' dynamics such that the multi-agent system can reach consensus in a distributed fashion. Our design approach is independent of the network topology and the agents can be used in mobile networks or fixed networks with different topologies. We review our previous result valid for fixed network topologies and extend it to the case when the interconnection among the nodes changes over time. In particular we focus on average consensus and consider undirected connected switching graphs. We establish the convergence property of the system by mode separation and an application of the small gain theorem.