9.1 Dial Backup
9.1.4
Example of dial backup for excessive traffic load
In the Figure, interface serial 0 is the primary interface. From the configuration in the Figure, you can tell that if the primary interface reaches a load threshold of 60 percent or higher, the backup interface (BRI 0) will be activated. The secondary line will deactivate after the primary line traffic load falls to within 5 percent of the primary lines bandwidth. The example in the Figure illustrates only the commands to enable a backup. The interface must also be configured as needed (for DDR, Frame Relay, X.25, and so on).
Lab Activity    
  You have just installed an ISDN line to be used as standby reserve bandwidth your Frame Relay connection between the Atlanta and Orlando office. Configure DDR on the BRI interface of the Orlando router. Configure Frame Relay on the serial interfaces connecting to the Frame Relay network. Configure parallel static routes so that when both links are up traffic will load balance between the two links.
Lab Activity    
  You have just installed an ISDN line to be used as standby reserve bandwidth for your Frame Relay connection between the Atlanta and Orlando office. Configure DDR using a dialer interface on the Orlando router. Configure Frame Relay on the serial interfaces connecting to the Frame Relay network. Configure this to work successfully with IGRP. EIGRP could also be used.