Motivated by routing in telecommunication network using Software Defined Network (SDN) technologies, we consider the following problem of finding short routing lists using aggregation rules. We are given a set of communications X , which are distinct pairs (s, t) ⊆ S × T , (typically S is the set of sources and T the set of destinations), and a port function π : X → P where P is the set of ports. A routing list R is an ordered list of triples which are of the form (s, t, p), If r(s, t) = π(s, t), then we say that (s, t) is properly routed by R and if all communications of X are properly routed, we say that R emulates (X , π). The aim is to find a shortest routing list emulating (X , π). In this paper, we carry out a study of the complexity of the two dual decision problems associated to it. Given a set of communication X , a port function π and an integer k, the A preliminary short version of this work has appeared in [7]. 2 Frédéric Giroire et al. first one called Routing List (resp. the second one, called List Reduction) consists in deciding whether there is a routing list emulating (X , π) of size at most k (resp. |X | − k). We prove that both problems are NP-complete. We then give a 3-approximation for List Reduction, which can be generalized to higher dimensions. We also give a 4-approximation for Routing List in the fundamental case when there are only two ports (i.e. |P | = 2), X = S × T and |S| = |T |.