Core Issue
Any interesting IP traffic, if not explicitly denied on a dialer list, brings up the dialer interface. Enhanced Interior Gateway Routing Protocol (EIGRP) hellos and updates act as interesting traffic and initiate an ISDN connection on a BRI if not explicitly denied in the interesting traffic list.
Resolution
Configure the ISDN as a backup link and configure the BRI or PRI interface(s) as passive interfaces under the respective routing protocol configuration, in this case EIGRP. Then configure a floating static route pointing to the BRI or PRI interface.
For more information, refer to Sample Configuration: Using Floating Static Routes and Dial-on-Demand Routing.
