9.2 Backup Interface Operations
9.2.2 Dialer profiles as backup interfaces
With dialer profiles, the BRI connection in the Figure can be used to back up the primary Frame Relay link between the central site and the branch office. At the same time, it can be configured for DDR between Branch Office A and Branch Office B (as shown in the Figure ). 

Configure one dialer profile to act as the backup line. This profile is in standby mode until engaged. Configure another dialer profile for legacy DDR between the Branch Office A and Branch Office B. Make the physical BRI interface a member of both dialer pools. When you use a BRI for a dial backup, neither of the B channels can be used while the interface is in standby mode. In addition, when a BRI is used as a backup interface and the BRI is configured for Legacy DDR, only one B channel is usable. After the backup is initiated over one B channel, the second B channel is unavailable. When the backup interface is configured for dialer profiles, both B channels can be used.