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Advanced DDR Operations 157

The troubleshooting section of this book could continue on indefinitely. However, the commands
here are only those that stay within the scope of the exam. For more information, go to
www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/dbook/index.htm and check
out the debug command reference.

Advanced DDR Operations

Up to this point, the discussion has been based in the basics of DDR. With a more solid
understanding of the technological base of ISDN and DDR implementations, it is now
appropriate to discuss some additional, and more advanced, features available with DDR.

DDR installations are capable of utilizing dialer profiles (utilizing virtual dialer interfaces) and
rotary groups. The installations also provide redundancy through dial backup and enable the use
of dynamic routes across a DDR link while maintaining the routing table and keeping the link
idle through snapshot routing.

Using Dialer Profiles

Dialer profiles first became a configuration option in Cisco IOS Release 11.2. The premise
behind dialer profiles was to enable flexible design capabilities for deployment of custom
profiles that meet users' dial access needs. This feature separates the logical function of DDR
from the physical interface that places or receives the calls.

Prior to dialer profiles, B channels had no choice but to take on the configuration options applied
to the physical interface. In this type of deployment, all users who dialed into a particular access
server received the same configuration, regardless of their access needs. With dialer profiles,
each user's needs can be met by customized services and unique interfaces. In other words, each
individual profile contains appropriately matched interface definitions and needs.

Dialer profiles enable the configuration of a logical interface to be associated with one or more
physical interfaces. With this type of deployment, the logical and physical configurations are
dynamically bound call by call. A dialer profile is made up of three components:

Dialer interfaces--Logical entities implementing a dialer profile on a destination-
by-destination basis. Destination specific settings are applied to the dialer interface
configurations. Multiple phone numbers (that is, dialer strings) can be specified for the
same interface. Using a dialer map class, multiple configuration variations can be
associated with a single phone number.

Dialer map class--Defines specific characteristics for any call made to the specified dial
string. Earlier in this chapter, the issue of rate adaptation was discussed. The configuration
examples specified the speed 56 parameter in the dialer map statement. With dialer
profiles, the map class can specify the speed based on the destination being dialed. At
other times, again based on destination, the map class can specify speed 64. The speed can
be altered on the fly based on the number being dialed. dialer map has an additional