Internet Service Providers (ISPs) can exploit path diversity to bal-ance load and improve robustness. Unfortunately, it is difficult to evaluate the potential impact of these approaches without routing and topological data, which are confidential. In this paper, we char-acterize path diversity in the real Sprint network. We then charac-terize path diversity in ISP topologies inferred using the Rocket-fuel tool. Comparing the real Sprint topology to the one inferred by Rocketfuel, we find that the Rocketfuel topology has signifi-cantly higher apparent path diversity. We evaluate heuristics that improve the accuracy of the inferred Rocketfuel topologies. Fi-nally, we discuss limitations of active measurements techniques to capture topological properties such as path diversity.