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Chapter 1 IP Telephony Deployment Models

Clustering Over the IP WAN

You may deploy a single Cisco CallManager cluster across multiple sites that are connected by an IP
WAN with QoS features enabled. This section provides a brief overview of clustering over the WAN.
For further information, refer to the section on

Call Processing, page 6-1

Clustering over the WAN can support two types of deployments:

Local Failover Deployment Model, page 1-17

Local failover requires that you place the Cisco CallManager subscriber and backup servers at the
same site, with no WAN between them. This deployment model is ideal for two or three sites with
Cisco CallManager servers and a maximum of 5000 or 2500 IP phones per site, respectively. This
model allows for up to 10,000 IP phones in the two-site configuration and 7,500 IP phones in the
three-site configuration.

Remote Failover Deployment Model, page 1-19

Remote failover allows you to deploy the backup servers over the WAN. Using this deployment
model, you may have up to six sites with Cisco CallManager subscribers and one or two sites
containing the Cisco CallManager backup server. This deployment allows for up to 10,000 IP
phones shared over the required number of sites.

Local Failover Deployment Model

The local failover deployment model provides the most resilience for clustering over the WAN. Each of
the sites in this model contains at least one primary Cisco CallManager subscriber and one backup
subscriber. This configuration allows for either a two-site deployment with 5000 IP phones per site or a
three-site deployment with 2500 IP phones per site. (See

Figure 1-5