When would you need this: When you are using ISDN links between more than two nodes.
Special Requirements: The router should have ISDN interface(s).
If you are implementing ISDN between two nodes only, you probably do not need to use this procedure, please refer to the BRI ISDN configuration procedure.
What the dialer profiles do is that it maps a dial string along with username to a certain destination. This way, the router knows what number to dial for different ISDN destinations using the same link. The main
problem that you may face without the use of dialer profiles is that the configuration is applied directly to the physical interface. This would cause that different logical links will need to use the same IP address and other configuration settings. The dialer profile applies the settings to the interface on on-call basis.
Multiple dialer interfaces may be configured on a router. Each dialer interface is the complete configuration for a destination. The ‘interface dialer’ command creates a dialer interface and enters interface configuration mode.
I will assume that you already set the switch-type and SPIDs, and start the configuration as the following:
1. Create a dialer-interface that contains the configuration of the interface to be used with a certain destination.
Router(config)#interface dialer X
where X is the dialer interface number that you may choose.
2. Configure the dialer interface as if you are configuring the regular DDR (refer to this procedure for more information). This configuration can be, IP address, encapsulation and authentication types, idle-timer, and dialer-group for interesting traffic. You can configure the encapsulation and authentication types on the physical interface later, if all of your connections use the same encapsulation and authentication types.
Read the rest of the article in the Router Geek Book: Guide to Cisco Routers Configuration