Configuring Loopback And Null Interfaces; Configuring A Loopback Interface; Introduction; Configuration Procedure - HP HSR6800 Configuration Manual

Configuring loopback and null interfaces

Configuring a loopback interface

Introduction

A loopback interface is a virtual interface. The physical layer state and link layer protocols of a loopback
interface are always up unless the loopback interface is manually shut down. A loopback interface is
widely used in the following scenarios:
A loopback interface address can be configured as the source address of the IP packets that the
•
device generates. Because loopback interface addresses are stable unicast addresses, they are
usually used as device identifications. When you configure a rule on an authentication or security
server to permit or deny packets that a device generates, you can simplify the rule by configuring
it to permit or deny packets carrying the loopback interface address that identifies the device.
When you use a loopback interface address as the source address of IP packets, make sure that the
peer is reachable through routes by performing routing configuration. All data packets sent to the
loopback interface are considered as packets sent to the device itself, so the device does not
forward these packets.
• A loopback interface is often used in dynamic routing protocols. For example, if no router ID is
configured for a dynamic routing protocol, the highest loopback interface IP address is selected as
the router ID. In BGP, to avoid BGP sessions being interrupted by physical port failure, you can use
a loopback interface as the source interface of BGP packets.

Configuration procedure

To configure a loopback interface:
Step
1. Enter system view.
2. Create a loopback interface
and enter loopback interface
view.
3. Set the interface description.
4. Shut down the loopback
interface.
5. Set the intended bandwidth for
the loopback interface.
6. Restore the default settings for
the loopback interface.
Command
system-view
interface loopback
interface-number
description text
shutdown
bandwidth bandwidth-value
default
84
Remarks
N/A
N/A
Optional.
By default, the description of a
loopback interface is interface name
Interface.
Optional.
By default, a loopback interface is up.
Optional.
Optional.