Designing CallManager Clusters
The powerful features offered by a CallManager cluster depend heavily on a good
design methodology. It is very important for you to have a good understanding of
the limitations, and Cisco recommendations, of CallManager clustering, in order to
design a quality IP telephony infrastructure.With this in place, you will be able to
provide a robust, efficient, and feature-rich IP telephony solution.
With Cisco CallManager 3.0(5) we are allowed a maximum of eight servers
per cluster, of which a maximum of six may be used for call processing.The
remaining two servers should be used as a database publisher server, and TFTP
server.These two roles may be combined on the same server, but it is recommended
they reside on separate servers for large installations.There can only be
one database publisher server, and one TFTP server per cluster.
Cisco recommends the guidelines shown in Table 4.2 when deciding upon the
configuration of a CallManager cluster. It is possible to use fewer servers, but
redundancy and load balancing will be reduced.The table also indicates the recommended
redundancy group configuration.A maximum of 2,500 IP phones, gateways,
and DSPs can be allocated to each CallManager with a maximum of 5,000
devices in total.
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