Troubleshooting Misconfigured Provider Switches

Unfortunately, when a problem exists with ISDN, your own site and the remote site are not the only areas you have to consider. Because this is a WAN-type issue, an administrator must consider the possibility that the service provider failed to configure the ISDN switch properly, particularly when this is a new installation.

To know when the local service provider's equipment may be the reason for a problem in the network, you should have a clear understanding of all the layers in which ISDN may be a problem. Those are Layers 1 through 3 of the OSI Reference model.