In network activation problems we are given a directed or undirected graph G = (V, E) with a family {fuv (xu, xv) : (u, v) ∈ E} of monotone non-decreasing activation functions from D2 to {0, 1}, where D is a constant-size domain. The goal is to find activation values xv for all v ∈ V of minimum total cost v∈V xv such that the activated set of edges satisfies some connectivity requirements. Network activation problems generalize several problems studied in the network literature such as power optimization problems. We devise an approximation algorithm for the fundamental problem of finding the Minimum Activation Cost Pair of Node-Disjoint st-Paths (MA2NDP). The algorithm achieves approxi