Configuration Example; Verifying Your Configuration - Cisco 520-T1 - Small Business Pro SR Secure Router Software Configuration Manual

Chapter 1 Basic Router Configuration
Perform these steps to configure a loopback interface, beginning in global configuration mode:
Command
Step 1
interface type number
Example:
Router(config)# interface Loopback 0
Router(config-if)#
ip address
Step 2
Example:
Router(config-if)# ip address 10.108.1.1
255.255.255.0
Router(config-if)#
Step 3 exit
Example:
Router(config-if)# exit
Router(config)#

Configuration 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
!

Verifying Your Configuration

To verify that you have properly configured the loopback interface, enter the show interface loopback
command. You should see verification output similar to the following example.
Router# show interface loopback 0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 200.200.100.1/24
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,
Encapsulation LOOPBACK, loopback not set
Last input never, output never, output hang never
OL-14210-01
ip-address mask
reliability 255/255, txload 1/255, rxload 1/255
Purpose
Enters configuration mode for the loopback
interface.
Sets the IP address and subnet mask for the
loopback interface.
Exits configuration mode for the loopback
interface and returns to global configuration mode.
Cisco Secure Router 520 Series Software Configuration Guide
Configuring Basic Parameters
1-7