External Call Routing

When you place a call from a Cisco IP Phone, Cisco CallManager analyzes the dialed digits. If the dialed number matches a directory number (DN) that is registered with the Cisco CallManager cluster, Cisco CallManager routes the call to the destination Cisco IP Phone that is associated with the matching DN. This type of call is an internal (or on-cluster) call. Cisco CallManager handles the call internally without the need to route the call to an external PSTN gateway.

IP Phones are not the only devices that can place and receive internal calls; any device that registers a DN with Cisco CallManager can place and receive internal calls. Examples of other devices include the Cisco IP SoftPhone/IP Communicator and analog telephones that are attached to Media Controller Gateway Protocol (MGCP) or Skinny Client Control Protocol (SCCP, or Skinny)based gateways.

When a Cisco IP Phone dials a number that does not match a registered DN, it assumes that the call is an external (or off-cluster) call. Cisco CallManager then searches its external route table to determine where to route the call. Cisco CallManager uses the concept of route pattern and translation pattern tables to determine where and how to route an external call. The route pattern and translation pattern tables are very similar to the routing table that a Cisco router maintains for routing data.

You can create external route plans based on a three-tiered architecture that allows multiple layers of call routing redundancy as well as digit manipulation. Route patterns match external dial strings, in which a corresponding route list will select available paths for the outbound call based on priority. Cisco refers to these paths as route groups, which are very similar to the trunk group concept in traditional PBX terminology. You can think of a route pattern as a static route with multiple paths that you can prioritize. Figure 10-1 depicts the three-tiered route plan architecture.

Figure 10-1. Cisco CallManager Route Plan Architecture

In addition to facilitating multiple prioritized paths for a given dialed number, the route plan can also provide unique digit manipulation for each path, based on the external network requirements. Digit manipulation involves adding or subtracting digits from the original dialed number to accommodate user dial habits and to ensure that the external network or PSTN receives the correct digits to place a call.

Even though the CallManager processes these route plans from the top down (a user dials the route pattern, which directs the call to a route list, then to the preferred route group, and finally to the device), the configuration of the route plan occurs from the bottom up (devices are added, route groups are created from the devices, route lists are created from the route groups, and the pattern points to the list).

Part I: Cisco CallManager Fundamentals

Introduction to Cisco Unified Communications and Cisco Unified CallManager

Cisco Unified CallManager Clustering and Deployment Options

Cisco Unified CallManager Installation and Upgrades

Part II: IPT Devices and Users

Cisco IP Phones and Other User Devices

Configuring Cisco Unified CallManager to Support IP Phones

Cisco IP Telephony Users

Cisco Bulk Administration Tool

Part III: IPT Network Integration and Route Plan

Cisco Catalyst Switches

Configuring Cisco Gateways and Trunks

Cisco Unified CallManager Route Plan Basics

Cisco Unified CallManager Advanced Route Plans

Configuring Hunt Groups and Call Coverage

Implementing Telephony Call Restrictions and Control

Implementing Multiple-Site Deployments

Part IV: VoIP Features

Media Resources

Configuring User Features, Part 1

Configuring User Features, Part 2

Configuring Cisco Unified CallManager Attendant Console

Configuring Cisco IP Manager Assistant

Part V: IPT Security

Securing the Windows Operating System

Securing Cisco Unified CallManager Administration

Preventing Toll Fraud

Hardening the IP Phone

Understanding Cryptographic Fundamentals

Understanding the Public Key Infrastructure

Understanding Cisco IP Telephony Authentication and Encryption Fundamentals

Configuring Cisco IP Telephony Authentication and Encryption

Part VI: IP Video

Introducing IP Video Telephony

Configuring Cisco VT Advantage

Part VII: IPT Management

Introducing Database Tools and Cisco Unified CallManager Serviceability

Monitoring Performance

Configuring Alarms and Traces

Configuring CAR

Using Additional Management and Monitoring Tools

Part VIII: Appendix

Appendix A. Answers to Review Questions


Authorized Self-Study Guide Cisco IP Telephony (CIPT)
Cisco IP Telephony (CIPT) (Authorized Self-Study) (2nd Edition)
ISBN: 158705261X
EAN: 2147483647
Year: 2004
Pages: 329

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