We present a formal framework to evaluate stochastic properties of MANET protocols. It captures the interplay between stochastic behavior of protocols deployed at different network layers, and the underlying dynamic topology. The link connectivity model, which implicitly models node mobility, specifies link up and down lifetimes. We use so-called constrained labeled multi-transition systems (CLMSs) to specify MANETs; transitions are annotated by network restrictions, capturing the topologies in which a transition is possible. A continuous Markov chain can be generated from a CLMS, to evaluate the performance of the corresponding MANET.