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Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter3 Configuring Cable Interface Features for the CiscouBR10012Router
Administratively Shutting Down and Restarting an Interface
Administratively Shutting Down and Restarting an Interface
You can disable an interface by shutting it down. Shutting down an interface disables all functions on
the specified interface and marks the interface as unavailable on the display of all monitoring commands.
This information is communicated to other network servers through all dynamic routing protocols. The
interface will not be mentioned in any routing updates. On serial interfaces, shutting down an interface
causes the dedicated Token Ring (DTR) signal to be dropped. On Token Ring interfaces, shutting down
an interface causes the interface to deinsert from the ring. On Fiber Distributed Data Interfaces (FDDIs),
shutting down an interface causes the optical bypass switch, if present, to go into bypass mode.
To shut down an interface and then restart it, use the following commands in interface configuration
mode:
To check whether an interface is disabled, use the show interfaces command in Privileged EXEC mode.
An interface that has been shut down is shown as administratively down in the show interfaces
command display.
One reason to shut down an interface is if you want to change the electrical interface type or mode of a
port online. You replace the serial adapter cable, for example, and use software commands to restart the
interface, and if necessary, to reconfigure the port for the new interface.
At system startup or restart, the Fast Serial Interface Processor (FSIP) polls the interfaces and determines
the electrical interface type of each port (according to the type of port adapter cable attached). However,
it does not necessarily poll an interface again when you change the adapter cable online.
To ensure that the system recognizes the new interface type, shut down the interface using the shutdown
command, and enable the interface after changing the cable. Refer to your hardware documentation for
more details.
Examples The following example turns off the Ethernet interface in slot 2 at port 4:
interface ethernet 2/4
shutdown
The following example restarts the interface:
interface ethernet 2/4
no shutdown
Command Purpose
shutdown Shuts down an interface.
no shutdown Enables an interface that has been disabled.