9.2 Backup Interface Operations
9.2.3 Configuring dial backup with dialer profiles
Dialer interfaces can be configured as the logical intermediary between physical interfaces. The dialer interface is the backup interface for the primary link. If the primary connection fails or is overutilized, the dialer interface kicks in and enlists a physical interface, typically BRI, to place the call.

To configure a dialer interface and a specific physical interface to function as backup to other physical interfaces, perform the following steps:

  1. Create and configure a dialer interface.
  2. The table in Figure reviews ways to configure a dialer interface. 
  3. Make the interface to be used as backup a member of the dialer pool by using the dialer pool member number command.
  4. You must then configure the primary interface to use a backup.
  5. Enter interface configuration mode for the primary interface.
  6. Assign an address to your interface.
  7. Specify the backup interface dialer to be used with the backup interface dialer number command.

Example shows the configuration of a site that backs up a leased line by using a BRI interface. One dialer interface, dialer 0, is defined. The leased line (serial 0) is configured to use the dialer interface (dialer 0) as a backup. The dialer interface uses dialer pool 1, which has physical interface BRI 0 as a member. Thus, physical interface BRI 0 can back up the serial interface.

Lab Activity
  You have been asked to implement a DDR dial backup link to backup the Frame Relay network between Orlando and Atlanta. You have installed an ISDN line in Orlando to make this possible. Now that Orlando has ISDN, you have come up with the idea to take advantage of that line so that you can connect to the Minneapolis office which also has an ISDN line. Configure a DDR connection between Orlando and Minneapolis. Because Orlando will be using the same line to connect to two different locations, you must use dialer profiles to make this possible.