9.1 Dial Backup
9.1.3
Activating a dial backup to support primary line traffic
You can configure a backup to activate the secondary line based on the traffic load on the primary line. The software monitors the traffic load and computes a five-minute moving average. If this average exceeds the value you set for the line (as shown in Figure ), the secondary line is activated. Depending on how the line is configured, some or all of the traffic will flow onto the secondary dialup line.

To configure backup if a primary line reaches or exceeds a certain threshold, perform the following steps:

  1. Select the primary interface and configure it as needed (for DDR, Frame Relay interfaces, X.25, and so on):

Router(config)#interface serial 0

  1. Use the following command on the primary interface to specify the backup to be used if a dial backup is needed:

Router(config-if)#backup interface interface-type number

  1. To set the traffic load threshold for dial backup service, use the following command syntax, which is explained in Table :

Router(config-if)#backup load {enable-threshold | never} {disable-threshold | never}

  1. The secondary line is disabled when one of the following conditions occurs:
  • The transmitted load on the primary line plus the transmitted load on the secondary line is less than the value entered for the disable-load argument.
  • The received load on the primary line plus the received load on the secondary line is less than the value entered for the disable-load argument.

The backup load command cannot be configured for Frame Relay subinterfaces.