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Dial-on-Demand Routing

What Does Dial-on-Demand Routing Mean?

Dial-on-Demand Routing (DDR) is a Cisco routing technique that initiates and closes circuit-switched data sessions on an automated and as-needed basis.


DDR uses external terminal adapters that enable wide area network (WAN) routing connections via Public Switched Telephone Networks (PSTN) or Integrated Services Digital Networks (ISDN).

Techopedia Explains Dial-on-Demand Routing

DDR enables remote WAN data connections that automatically terminate after transmission activity ends. DDR is used with primary and backup connections.

DDR connectivity is established in either of the following ways:

Physical: A cable connects the PSTN to the computer’s network interface card (NIC) for user communication.
Digital: Point-to-Point Protocol (PPP) determines a connection logic for network signal function management (sending, receiving, compression).

DDR provides a range of configuration commands, including:

Phone companies establish connection switch types and local exchange termination points. Configuration depends on traffic setup triggers specified by standard or extended interface dialer access lists (like interesting traffic).

Static routing remains constant to facilitate local and remote bidirectional reachability.
During ISDN installation, PPP or High-Level Data Link Control (HDLC) enables encapsulation.

After encapsulation, the host address implements IP addressing that is hard coded during global configuration or extracted from the local area network (LAN) interface address with the lowest number.


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