| 9.3 |  | Troubleshooting Router Issues Overview |
| 9.3.6 |  | Troubleshooting using show controllers serial |

| Very often, configuration and troubleshooting on routers is done remotely when it is not possible to physically inspect the router connections. The show controllers serial command is useful to determine the type of cable connected without inspecting the cables. By examining the show controllers serial command output, the type of cable that the controller detects can be determined. This is useful for finding a serial interface with no cable, the wrong type of cable, or a defective cable. The show controllers serial command queries the integrated circuit (chip) that controls the serial interfaces and displays information about the physical interface. This output varies from controller chip to controller chip. Even within a router type, different controller chips may be used. Regardless of the controller type, the show controllers serial command produces a tremendous amount of output. Other than the cable type, most of this output is internal technical detail regarding the controller chip status. Without specific knowledge of the integrated circuit, this information is of little use.
| Lab Activity e-Lab Activity: Troubleshooting Using show controllers serial In this lab, the students will use the show controllers command to see what cable is attached to the serial interface.
| Web Links show controllers serial Command http://www.cisco.com/en/US/products/sw/ iosswrel/ps1835/ products_command_reference_ chapter09186a00800874c2.html#1019005