MPLS is simple to configure and troubleshoot. Not many things can go wrong, and recent IOS versions (such as IOS release 12.2) check most of the prerequisites for successful MPLS operation before MPLS-related configuration commands can be entered.
MPLS is so transparent in simple IP networks that do not use advanced MPLS features (such as BGP running only on the edge routers) or MPLS applications (MPLS VPNs or MPLS-TE) that it is sometimes hard to detect that MPLS is not operational. The first problems usually arise when you are trying to deploy advanced MPLS features.
If you encounter MPLS-related problems in your network, you should check the following things first. (The next section contains detailed ...