Editing Dial-on-demand routing (section)

==Dialer maps and rotary groups==

Dialer maps are configured on each interface to specify which numbers to dial and how long to stay on the line waiting for the receiving end to pick up. For example, if two dialer map commands on the [[Serial Interface]] 0/0/0 (Serial port 0 of module 0 of interface 0) have the same next hop address, or the IP address of the connection at the destination end, but with different phone numbers, then the first number is dialed and only once the wait-for-carrier timer expires will the next number be dialed. The wait-for-carrier timer can be specified when configuring the dialer map.

Backup interfaces can also be defined in the event that all of the numbers on a dialer map for that interface were unreachable. A single interface can be configured for multiple remote sites because no two connections to one interface can be on at the same time. The first step in specifying a DDR interface is defining a rotary group. Although the DDR interface is a virtual one, all of the configuration commands for physical interfaces are available. A dialer Rotary Group can be created so that either of the interfaces in it can be used to dial any of the destinations defined in it.<ref>Dial-on-Demand Routing (DDR) - Cisco Systems. (n.d.). . Retrieved March 2, 2010, from http://www.cisco.com/en/US/tech/tk801/tk133/tsd_technology_support_protocol_home.html</ref>