Route asymmetry is detected in a network by running a route tracing program to trace routes between a first element of the network and a second element of the network. The route tracing program need be run at only a single network element, such as the first network element. Forward and reverse routes between the first and second network elements are identified as asymmetric if performance data from the route tracing program indicates a significant deviation from an expected monotonic characteristic as a function of time-to-live values of respective packets transmitted by the route tracing program.