6.1 Dialer Rotary
6.1.1 Creating and configuring a rotary group
Dialer rotary groups simplify the configuration of physical interfaces by allowing you to apply a single logical interface configuration to a set of physical interfaces . The single logical interface is a dialer rotary group, which is defined by specifying a dialer interface. Physical interfaces are assigned to the dialer rotary group and inherit all the dialer interface configuration parameters. When many destinations are configured, any of the physical interfaces in a rotary group can be used for outgoing calls.

To configure a rotary group, you place each Basic Rate Interface (BRI) interface in a rotary group. In Figure , all the BRIs are assigned to dialer rotary-group 1. All these BRI lines are also set in a hunt group. A hunt group is a series of telephone lines that are programmed so that as incoming calls arrive, if the first line is busy, the second line is tried, and then the third line is tried, and so on until a free line is found. This way, an incoming call should not end up with a busy signal.

You may still have to perform some of the configuration on the physical interface rather than at the dialer rotary interface. For example, if you connect to a switch that requires service profile identifiers (SPIDs), you have to enter each of the SPIDs separately at each of the physical BRI interfaces. The rest of the interface configuration is done on the interface dialer 1, the new rotary you created.

If you install multiple BRIs or (Primary Rate Interfaces (PRIs) to service remote users, request one phone number from the service provider. You then assign all the interfaces to one rotary group, or hunt group, so that you need to dial only one number for either configuration. Using one number requires only one set of dialer-map statements on the remote routers instead of multiple statements, a scenario that also makes configuration and debugging much easier and less complicated.

The interface dialer command in global configuration mode creates a dialer rotary group:

Router(config)#interface dialer group-number

Then, you use the dialer rotary-group command in interface (BRI, async, and so on) configuration mode to include that interface in the specified rotary group, as shown in the syntax that follows. You have to use this command on each interface that you wish to include in the rotary group.

Router(config-if)#dialer rotary-group group-number

The syntax for the interface dialer and dialer rotary-group commands are explained in Table .