Once a leased line has been properly provisioned and installed by the telco, installation of a WAN network using Cisco routers is usually a simple, trouble-free task, requiring minimal configuration and maintenance. However, when a network does not operate as expected, proven problem-isolation techniques can be applied to recognize and solve common WAN problems.
Cisco routers offer diagnostic tools to assist in troubleshooting network problems.
This document specifically focuses on how the show interface command can be used to diagnose serial interfaces in a leased line environment. Important fields for diagnosing serial line problems are outlined in the illustration and explained below. The quickest way to diagnose the functionality of a serial interface is to read the first line of the show interfaces serial output. This status indicates that the interface is functioning properly. Step 4 Contact your leased-line or other carrier service.