down-when-looped — interface
down-when-looped no down-when-looped
This command tells the interface to go down when a loopback is detected. The default behavior is for the interface to remain up when the device is placed in loopback, so you can place a DCE device such as a CSU/DSU in loopback and ping the interface. This allows you to test the cable between the router and the DCE device.
no form of this command to disable this behavior. If this command is given, the interface shuts down when the DCE device (CSU/DSU) is placed in loopback mode.