The distributed nature of the Internet makes it difficult for a single service provider to troubleshoot the disruptions ex-perienced by its customers. We propose NetDiagnoser, a troubleshooting algorithm to identify the location of failures in an internetwork environment. First, we adapt the well-known Boolean tomography technique to work in this envi-ronment. Then, we significantly extend this technique to im-prove the diagnosis accuracy in the presence of multiple link failures, logical failures (for instance, misconfigurations of route export filters), and incomplete topology inference. In particular, NetDiagnoser takes advantage of rerouted paths, routing messages collected at one provider's network and Looking Glass servers. We evaluate each feature of Net-Diagnoser separately using C-BGP simulations on realistic topologies. Our results show that NetDiagnoser can success-fully identify a small set of links, which almost always in-cludes the actually failed/misconfigured links.