Dialer rotary groups are designed to simplify configuration for multiple callers and multiple-destination environments by binding a single configuration to multiple physical interfaces. Synchronous, asynchronous, ISDN BRI, and ISDN PRI interfaces can make up a dialer rotary group. A physical interface that is configured as a member of a rotary group assumes configuration parameters for the group. A rotary group consisting of multiple physical interfaces applies the configuration of a logical dialer interface, also called a virtual dialer interface, to all its members.

When rotary groups are used, such characteristics as the IP address, interesting traffic definition, and call parameters are connected with the dialer interface rather than the physical interface. When a call comes into the router, the dialer interface selects a physical interface from the pool of physical interfaces.

With rotary groups, users of several BRIs or PRIs might get a single phone number from the service provider. Therefore, they allocate all their interfaces to a single rotary group so that only one number needs to be dialed. This kind of setup requires the remote routers to have only one set of dialer map statements for your destination. In turn, debugging and management on the user side are less complicated.

This tutorial is divided into two portions:

• Configuring dialer profiles

• Configuring dialer rotary groups

Each part briefly describes the general configuration tasks involved in setting up dialer profiles and rotary groups.

Configuring Dialer Profiles

Dialer profile configuration involves three separate stages:

Let's briefly look at some commands that let you configure dialer profiles. A number of commands involved in this process create relationships between the elements of a dialer pool. Some of these commands belong to the physical interface configuration portion, and others belong to the dialer interface.

Among the dialer interface commands is the dialer string command, which specifies the destination's phone number. Multiple phone numbers may be included using dialer string. Starting with Cisco IOS Release 12.2(8)T, you can specify the order in which these phone numbers are to be used. Within the dialer string command, you can include the optional keyword class, followed by the map-class-name parameter. When used, they specify a particular map class and pull the configurations from that map class for the call.

Another portion of the dialer profile configuration is to specify the pool of physical interfaces used to reach the target network. The pool is identified by a number between 1 and 255.

To make your configuration completely functional, two extra steps need to be taken:

Configuring Dialer Rotary Groups

Five configuration stages set up dialer rotary groups: