A method, system and diagnostic tool for diagnosing a problem in CSPF and non-CSPF MPLS networks, including problems with LDP tunnels. This includes one or more of the following: hopping from network element to network element; determining whether an LSP between elements is operational; determining whether the hop was strict or loose; evaluating whether there is an existing path between the elements; finding and remembering an IGP link between the elements; recognizing whether the LSP is an FRR LSP; diagnosing a cause of the LSP between the elements being down; and altering a display of a topology map of the network to indicate the cause of the problem.