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Collaboration, Voice & AV · Advanced

Clustering over the WAN

A CUCM deployment model that places cluster nodes at different sites, requiring a maximum of 80 ms round-trip delay between servers.

Definition

Clustering over the WAN distributes subscribers across data centers so phones can register locally while sharing one configuration. Cisco design guidance limits intracluster round-trip time to 80 ms and requires sufficient bandwidth for database replication and intracluster signaling. Alternatives are a single centralized cluster or multiple distributed clusters connected by trunks.

Example

Subscribers in New York and Chicago belong to one cluster connected by a 20 ms RTT WAN link.

Exam tip

The key number is 80 ms RTT between nodes; exceeding it calls for separate clusters joined by SIP trunks or SME.

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