Administrator Guide

Loopback Interfaces
A Loopback interface is a virtual interface in which the software emulates an interface. Packets routed to it are processed
locally.
Because this interface is not a physical interface, you can configure routing protocols on this interface to provide protocol
stability. You can place Loopback interfaces in default Layer 3 mode.
To configure, view, or delete a Loopback interface, use the following commands.
● Enter a number as the Loopback interface.
CONFIGURATION mode
interface loopback number
The range is from 0 to 16383.
● View Loopback interface configurations.
EXEC mode
show interface loopback number
● Delete a Loopback interface.
CONFIGURATION mode
no interface loopback number
Many of the commands supported on physical interfaces are also supported on a Loopback interface.
Null Interfaces
The Null interface is another virtual interface. There is only one Null interface. It is always up, but no traffic is transmitted
through this interface.
To enter INTERFACE mode of the Null interface, use the following command.
● Enter INTERFACE mode of the Null interface.
CONFIGURATION mode
interface null 0
The only configurable command in INTERFACE mode of the Null interface is the ip unreachable command.
Configuring Port Delay
To configure a delayed bring up of all interfaces during switch boot up, use the following command:
● Enter the CONFIGURATION mode.
CONFIGURATION mode
Use the port-delay-restore command and ensure to specify a value between 1 second and 300 seconds.
DellEMC(conf)#port-delay-restore 300
Use the no port-delay-restore command to disable the feature.
DellEMC(conf)#no port-delay-restore
If you would like to turn this feature off for an individual interface, enter the INTERFACE mode and use the no port-delay-
restore command.
DellEMC(config-if)#no port-delay-restore
NOTE:
● This command does not work on the Port Extender ports.
426 Interfaces