4000 Router Series Layer 2 - WAN Configuration Guide

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Configuring B-DDR

In the B-DDR approach, physical interface configuration is separated from logical configuration for calls,

and they can be combined dynamically for each call.

When you configure B-DDR for on-demand dial, configure B-DDR sets. Each B-DDR set is an attribute

collection containing a dialer interface, dialer interface attributes, and a dialer bundle.

• For each dialer interface, you can define only one dial string. Because this dial string has its own

dial attribute set, all calls placed by using this dial string use the same DDR attribute parameters

(such as dial rate).

• Each dialer interface can use only one dialer bundle. Each dialer bundle can contain multiple

physical interfaces with different priorities, and each of these interfaces can belong to multiple

dialer bundles. For an ISDN BRI or PRI interface, you can set the number of B channels to be used

by configuring the dialer bundle command.

• All calls destined to the same network segment use the same B-DDR set.

Due to the separation between physical configuration and logical configuration, B-DDR can

accommodate more network topologies and DDR dial demands. For example, it allows multiple

interface groups to call multiple remote ends.

Figure 40 Multiple interfaces call multiple remote ends in B-DDR approach

In this scenario, a dialer interface is configured only for calling one remote end. On-demand dial, in this

case, is implemented by assigning a physical interface to dialer bundles associated with different dialer

interfaces.

If B-DDR sets are used to configure B-DDR parameters, you only need to configure link layer

encapsulation and dialer bundle numbers on physical interfaces.

Before you configure B-DDR, follow these guidelines:

• At the initiator end, a physical interface uses the configuration of the dialer interface (known) to

place calls (including PPP negotiation). Therefore, configure PAP or CHAP authentication on the

dialer interface, if necessary.

• At the receiving end, the dialer interface to be used for the physical interface cannot be determined

before PPP authentication. It is determined by checking the authentication username against the

dialer peer-name commands configured on the dialer interfaces to which the physical interface

belong. Then, PPP uses the configuration of the matching dialer interface for IPCP negotiation.

Therefore, you should configure PAP or CHAP authentication on the physical interface and the

dialer peer-name command on dialer interfaces.