Chapter 3 Basic Router Configuration

Configuring a Loopback Interface

Configuring a Loopback Interface

The loopback interface acts as a placeholder for the static IP address and provides default routing information.

To configure a loopback interface perform these steps, beginning in global configuration mode:

SUMMARY STEPS

1.interface type number

2.ip address ip-address mask

3.exit

 

DETAILED STEPS

 

 

 

 

 

Command

Purpose

 

 

 

Step 1

interface type number

Enters configuration mode for the loopback

 

Example:

interface.

 

 

 

Router(config)# interface Loopback 0

 

 

Router(config-if)#

 

 

 

 

Step 2

ip address ip-address mask

Sets the IP address and subnet mask for the

 

 

loopback interface.

 

Example:

 

 

Router(config-if)# ip address 10.108.1.1

 

 

255.255.255.0

 

 

Router(config-if)#

 

 

 

 

Step 3

exit

Exits configuration mode for the loopback

 

 

interface and returns to global configuration

 

Example:

mode.

 

Router(config-if)# exit

 

 

Router(config)#

 

 

 

 

Example

The loopback interface in this sample configuration is used to support Network Address Translation (NAT) on the virtual-template interface. This configuration example shows the loopback interface configured on the Fast Ethernet interface with an IP address of 200.200.100.1/24, which acts as a static IP address. The loopback interface points back to virtual-template1, which has a negotiated IP address.

!

interface loopback 0

ip address 200.200.100.1 255.255.255.0 (static IP address) ip nat outside

!

interface Virtual-Template1 ip unnumbered loopback0

no ip directed-broadcast ip nat outside

!

 

 

Cisco 880 Series Integrated Services Router Software Configuration Guide

 

 

 

 

 

 

OL-22206-01

 

 

3-17

 

 

 

 

 

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Cisco Systems CISCO881SECK9 manual Configuring a Loopback Interface, Exit

CISCO881SECK9 specifications

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