Cisco Systems OL-6426-02 Benutzerhandbuch

The Cisco 1800 integrated services fixed-configuration routers support dial-in (for remote management) 
and dial-out (for dial backup) capabilities. By allowing you to configure a backup modem line 
connection, the Cisco 1800 integrated services fixed-configuration routers provide protection against 
WAN downtime. Dial backup is inactive by default, and must be configured to be active.

Dial backup and remote management functions are configured through the ISDN S/T port of the 
Cisco 1812, Cisco 1801, Cisco 1802, and Cisco 1803 routers. These functions are configured through 
the V.92 modem port of the Cisco 1811 router.

This chapter contains the following topics:

Three methods are available to activate the dial backup feature:

When the router receives an indication that the primary line is down, a backup interface is brought up. 
You can configure the backup interface to go down once the primary connection has been restored for a 
specified period.

This is accomplished using dial-on-demand routing (DDR). When this is configured, a backup call is 
triggered by specified traffic.