Configuring a Loopback Interface

A loopback interface has the following features:

Based on the preceding features, the loopback interface has the following applications.

The IP address of a loopback interface is specified as the source address of packets to improve network reliability.
When no Router ID is configured for dynamic routing protocols, the maximum IP address of the loopback interface is automatically configured as the router ID.
The loopback interface is configured as the source interface to send boarder gateway protocol (BGP) packets to ensure that the BGP session functions properly when the physical interface is faulty.
The loopback interface can be configured with the mask of 255.255.255.255 to save IP address resources.
The loopback interface can be assigned an IPv4 address and configured to check the source IPv4 addresses of packets.

Before configuring a loopback interface, power on the device and perform self-check.

Run system-view
The system view is displayed.
Run interface loopback loopback-number
A loopback interface is created and the loopback interface view is displayed.

You can create or delete a loopback interface dynamically. After a loopback interface is created, the link-layer protocol is always Up unless the loopback interface is deleted.
Run ip address ip-address { mask | mask-length } [ sub ]
The IP address of the loopback interface is configured.
(Optional) Run ip verify source-address
The loopback interface is configured to check the source IPv4 addresses of packets.

Run the display interface loopback [ loopback-number ] command to check the status of a loopback interface.