Dial-on-Demand Routing

  • Dial-on-Demand routing refers to a collection of Cisco features that allows two or more Cisco routers to establish a dynamic connection over simple dialup facilities on an as-needed basis and is used for low-volume, periodic network connections over an ISDN network or Public Switched Telephone Network.
    There are five basic steps of DDR operation:

    1. The route to the destination is determined
    2. Interesting packets dictate a DDR call
    3. The dialer information is looked up
    4. Traffic is transmitted
    5. The call is terminated
  • There are three stages for configuring legacy DDR:

    1. Define the static route
    2. Specify interesting traffic
    3. Configure the dialer information
  • When using static routes, all participating routers must have static routes defined so that they can reach the remote networks. This requirement is necessary because static routes replace routing updates
  • Interesting traffic, which triggers a DDR call, is designated by an administrator and can be defined on the basis of a variety of criteria, such as protocol type or addresses for source or destination hosts.
  • The dialer information configuration process consists of four steps:

    1. Select the physical interface for the dial-up line
    2. Configure its network address
    3. Configure the encapsulation type
    4. Link the interesting traffic definition to the interface
  • To configure legacy DDR, define the static routes with the, ip route command, specify interesting traffic with the dialer list command, and configure dialer information with the dialer group command

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