This example sets up a modem dial backup for the WAN link between a branch office and the headquarters data center. The branch office is connected to the corporate network using a Branch Gateway. IP phone users in the branch office connect to an MGC located in the headquarters data center, and an RAS is located in the headquarters data center, with multiple phone lines available for dial access. The primary WAN connection is a broadband link connected to the WAN FastEthernet port. The Dialer PPP session uses CHAP encryption. The corporate network is routed using OSPF. An analog trunk connects the branch office to the PSTN for non-corporate bearer traffic.

The following figure shows the network topology.