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Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
OL-20696-04
Chapter       Configuring Backup Data Lines and Remote Management
Configuring Backup Interfaces
DETAILED STEPS
Cellular Wireless Modem as Backup with NAT and IPSec Configuration
The following example shows how to configure the 3G wireless modem as backup with NAT and IPsec 
on either GSM or CDMA networks.
Note The receive and transmit speeds cannot be configured. The actual throughput depends on the cellular 
network service.
Router# sh run
Building configuration...
Current configuration : 5833 bytes
!
! Last configuration change at 18:26:15 UTC Wed Sep 30 2009
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
service internal
!
hostname Router
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
!
!
service-module wlan-ap 0 bootimage autonomous
!
no ipv6 cef
ip source-route
ip cef
!
!
ip multicast-routing 
Command or Action Purpose
Step 1
configure terminal 
Example:
Router# configure terminal
Enters global configuration mode from the terminal. 
Step 2
ip route network-number network-mask {ip-address | 
interface} [administrative-distance] [name name]
Example:
Router (config)# ip route 0.0.0.0 Dialer 2 track 234
Establishes a floating static route with the 
configured administrative distance through the 
specified interface. 
A higher administrative distance should be 
configured for the route through the backup 
interface, so that the backup interface is used only 
when the primary interface is down.