Configuring Intercluster Trunks

Table of contents:

Although the SQL 2000 database shared between CallManagers in your cluster provides a listing of all extensions that a user can dial within the cluster, you must manually add connections and route patterns to remote clusters before they can be reached. The connection type that acts as the road between CallManager clusters is the intercluster trunk. Depending on the size of your IP telephony network, you can create trunks directly between CallManager clusters or you can create trunks to connect to an H.323 gatekeeper.


You can create a network of enormous size using only intercluster trunks; however, because the trunks are a full-mesh configuration, it can become increasingly difficult to manage the larger your network gets. Intercluster trunks also lack the ability to perform call admission control, which could result in the WAN becoming swamped with VoIP traffic.

A gatekeeper provides call admission control by using the H.225 Registration, Admission, and Status (RAS) protocol message set that is used as a central point for call admission control, bandwidth allocation, and dial pattern resolution (call routing). The gatekeeper provides these services for communications between Cisco CallManager clusters and H.323 networks. Note that the voice path is between the endpoints; no RTP audio travels through the gatekeeper.

You can configure gatekeepers and trunks in Cisco CallManager Administration to function in either of the following ways:

  • Nongatekeeper-controlled trunks In this case, you explicitly configure a separate Intercluster Trunk for each remote device cluster that the local Cisco CallManager can call over the IP WAN, as shown in Figure 9-4. You also configure the necessary dial plan details to route calls to and from the various Intercluster Trunks. The Intercluster Trunks statically specify the IP addresses of the remote devices. To use this method, choose Device > Trunk and then choose Inter-Cluster Trunk (Non-Gatekeeper Controlled) in Cisco CallManager Administration.

    Figure 9-4. Nongatekeeper-Controlled Trunk Design

  • Gatekeeper-controlled trunks In this case, a single intercluster trunk from each CallManager cluster suffices for communicating with all remote clusters, as shown in Figure 9-5. Similarly, you need only a single H.225 trunk to communicate with multiple H.323 gatekeeper-controlled endpoints. In this configuration, the gatekeeper can dynamically determine the appropriate IP address for the destination of each call to a remote device, and the local Cisco CallManager uses that IP address to complete the call.

    Figure 9-5. Gatekeeper-Controlled Trunk Design

    This configuration works well in large and smaller systems. For large systems in which many clusters exist, this configuration helps to avoid the configuration of individual Intercluster Trunks between each cluster. To use this method, choose Device > Trunk and choose Inter-Cluster Trunk (Gatekeeper Controlled) in Cisco CallManager Administration.

    If you configure gatekeeper-controlled trunks, Cisco CallManager automatically creates a virtual trunk device. The IP address of this device changes dynamically to reflect the IP address of the remote device as determined by the gatekeeper.

Complete these steps to configure a nongatekeeper-controlled intercluster trunk:

Step 1.

Choose Trunk from the Device menu in the Cisco CallManager Administration window.

Step 2.

Click the Add a New Trunk link and choose Inter-Cluster Trunk (Non-Gatekeeper Controlled) from the Trunk Type drop-down menu.

Step 3.

Cisco CallManager populates the Device Protocol field with the appropriate protocol. Click Next to continue.

Step 4.

The Trunk Configuration window appears, as shown in Figure 9-6. Add the device name. It does not have to be the IP address, but it must be unique throughout the cluster.

Figure 9-6. CallManager Nongatekeeper-Controlled intercluster trunk Configuration


Step 5.

At the bottom of the Trunk Configuration window, you can add the IP addresses of up to three Cisco CallManager servers in the remote cluster. You must add the IP address for at least one remote CallManager.


Configuring gatekeeper-controlled intercluster trunks is covered in Chapter 14, "Implementing Multiple-Site Deployments."

SIP and Cisco CallManager

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 © 2008-2020.
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